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1. ooo a 73 8 2 19 2 When does kea dhcp6 generate DDNS request o o 73 8 2 19 3 kea dhcp6 name generation for DDNS update requests o o 75 8 3 Host reservation in DHCPv6 2 20 2 000 2 ee ee 76 8 3 1 Address prefix reservation types 2 Te 8 3 2 Conflicts in DHCPv6 reservations a TT 8 3 3 Reserving a hostname aoaaa a 78 8 3 4 Reserving specific options 2 19 8 3 5 Fine Tuning IPv6 Host Reservation ee ee 79 8 4 Server Identifier in DHCPV6 2 c spos e os BAG BR eRe Ae ew A a oe e 79 8 5 Stateless DHCPv6 Information Request Message ooa e 80 8 6 Using specific relay agent for a subnet nooo 0 00000000222 eee eee 80 8 7 Segregating IPv6 clients in a cable network ee 81 8 8 MAC Hardware addresses in DHCPv6 ee 82 8 9 Statistics in DHCPv6 server ee 83 8 10 Management API for the DHCPv6 server 2 ee 83 8 11 Supported DHCPv6 Standards ee 83 8 12 DHCPv6 Server Limitations 2 2 2 0 0 2 0 002000222 ee 85 9 The DHCP DDNS Server 86 9 1 Starting and Stopping the DHCP DDNS Server 86 9 2 Configuring the DHCP DDNS Server 0 002000 00002 eee ee 87 9 2 1 Global Server Parameters pe sopeuttaa eR RE GR RES a EL RE E 88 92 2 TSIG Key List ias gate Sk Gs Ba ae a Ae eR ee a ee Ae RO BOE e 88 9 23 Forward DDNS cios alae e he Rak Re De ar A EE Rl oe ee ee as 89 9 2 3 1 Addin
2. Name Meaning binary An arbitrary string of bytes specified as a set of hexadecimal digits boolean Boolean value with allowed values true or false empty No value data is carried in suboptions fqdn Fully qualified domain name e g www example com ipv4 address IPv4 address in the usual dotted decimal notation e g 192 0 2 1 ipv6 address IPv6 address in the usual colon notation e g 2001 db8 1 Structured data that may comprise any types except ESO record and empty string Any text uint8 8 bit unsigned integer with allowed values 0 to 255 uintl6 16 bit unsigned integer with allowed values 0 to 65535 uint32 32 bit unsigned integer with allowed values 0 to 4294967295 Table 7 3 List of standard DHCP option types Kea Administrator Reference Manual 34 113 New options can take more complex forms than simple use of primitives uint8 string ipv4 address etc it is possible to define an option comprising a number of existing primitives Assume we want to define a new option that will consist of an IPv4 address followed by an unsigned 16 bit integer followed by a boolean value followed by a text string Such an option could be defined in the following way Dhcp4 Vopr ion deruk a name bar code 223 space dhcp4 type record array false record types ipv4 address uint16 boolean string encapsulate The type is set to rec
3. Ie It is anticipated that this will form of usage only be used where it is desired to temporarily override a list of interface names and listen on all interfaces 8 2 4 IPv6 Subnet Identifier The subnet identifier is a unique number associated with a particular subnet In principle itis used to associate clients leases with respective subnets When the subnet identifier is not specified for a subnet being configured it will be automatically assigned by the configuration mechanism The identifiers are assigned from 1 and are monotonically increased for each subsequent subnet L2 3x If there are multiple subnets configured with auto generated identifiers and one of them is removed the subnet identifiers may be renumbered For example if there are four subnets and the third is removed the last subnet will be assigned the identifier that the third subnet had before removal As a result the leases stored in the lease database for subnet 3 are now associated with subnet 4 which may have unexpected consequences In the future it is planned to implement a mechanism to preserve auto generated subnet ids upon removal of one of the subnets Currently the only remedy for this issue is to manually specify a unique subnet identifier for each subnet The following configuration will assign the specified subnet identifier to the newly configured subnet UDEG te xf subnet6 SUBS O O Se e id 1024 This identifier will not change for
4. Kea Administrator Reference Manual 35 113 DRC PATEE UeiieaoueKsice 3 name foo code 1 space vendor encapsulated options space type record array false record types ipv4 address uint16 string encapsulate Note that the option space is set to vendor encapsulated options space Once the option format is defined the next step is to define actual values for that option DEA Ukeyore aon Glace name foo space vendor encapsulated options space code 1 csv format true data 192 0 2 3 123 Hello World We also include the Vendor Specific Information option the option that conveys our sub option foo This is required else the option will not be included in messages sent to the client Macrae if Teieskom Cleice 3 name vendor encapsulated options Alternatively the option can be specified using its code IDC Topreikon dao code 43 7 2 10 Nested DHCPv4 Options Custom Option Spaces It is sometimes useful to define completely new option space This is the case when user creates new option in the standard option space dhcp4 and wants this option to convey sub options Since they are in a separate space sub option codes will have a separate numbering scheme and may overlap with the codes of standard options Kea Administrator Reference Manual 36 113 Note that creation of a new option space when defining sub options fo
5. Mo if Tojo srom claiev e name bar code 101 space dhcp6 type record array false record types ipv4 address uint16 boolean string encapsulate The type is set to record to indicate that the option contains multiple values of different types These types are given as a comma separated list in the record types field and should be those listed in Table 7 3 The values of the option are set as follows iDance ts i Vopr ion darane name bar 5 space dhcp6 code 101 csv format true data 2001 db8 1 10 123 false Hello World Kea Administrator Reference Manual 66 113 csv format is set true to indicate that the data field comprises a command separated list of values The values in the data must correspond to the types set in the record types field of the option definition Note In the general case boolean values are specified as true or false without quotes Some specific boolean parameters may accept also true false 0 1 0 and 1 Future Kea versions will accept all those values for all boolean parameters 8 2 10 DHCPv6 vendor specific options Currently there are two option spaces defined for the DHCPv6 daemon dhcp6 for top level DHCPv6 options and vendor opts space which is empty by default but options can be defined in it Those options will be carried in the Vendor specific Information option code 17 The foll
6. dhcp6 csv format true data 2001 db8 1 3 de The currently supported standard DHCPv6 options are listed in Table 8 1 The Name and Code are the values that should be used as a name in the option data structures Type designates the format of the data the meanings of the various types is given in Table 7 3 Some options are designated as arrays which means that more than one value is allowed in such an option For example the option dns servers allows the specification of more than one IPv6 address allowing clients to obtain the addresses of multiple DNS servers The Section 8 2 9 describes the configuration syntax to create custom option definitions formats It is generally not allowed to create custom definitions for standard options even if the definition being created matches the actual option format defined in the RFCs There is an exception from this rule for standard options for which Kea does not provide a definition yet In order to use such options a server administrator must create a definition as described in Section 8 2 9 in the dhcp6 option space This definition should match the option format described in the relevant RFC but the configuration mechanism would allow any option format as it has no means to validate the format at the moment 8 2 9 Custom DHCPv6 options It is also possible to define options other than the standard ones Assume that we want to define a new DHCPv6 option called foo which w
7. space isc data Hello world name container code 222 space dhcp4 Note that it is possible to create an option which carries some data in addition to the sub options defined in the encapsulated option space For example if the container option from the previous example was required to carry an uint16 value as well as the sub options the type value would have to be set to uint16 in the option definition Such an option would then have the following data structure DHCP header uint16 value sub options The value specified with the data parameter which should be a valid integer enclosed in quotes e g 123 would then be assigned to the uint16 field in the container option 7 2 11 Unspecified parameters for DHCPv4 option configuration In many cases it is not required to specify all parameters for an option configuration and the default values may be used However it is important to understand the implications of not specifing some of them as it may result in configuration errors The list below explains the behavior of the server when a particular parameter is not explicitly specified e name the server requires an option name or option code to identify an option If this parameter is unspecified the option code must be specified e code the server requires an option name or option code to identify an option This parameter may be left unspecified if the name parameter is specified However
8. These steps would be repeated for each TSIG key needed Note that the same TSIG key can be used with more than one domain 9 2 3 Forward DDNS The Forward DDNS section is used to configure D2 s forward update behavior Currently it contains a single parameter the catalog of forward DDNS Domains which is a list of structures UDne DD Cans el forward_ddns ddns_domains By default this list is empty which will cause the server to ignore the forward update portions of requests Kea Administrator Reference Manual 90 113 9 2 3 1 Adding Forward DDNS Domains A forward DDNS Domain maps a forward DNS zone to a set of DNS servers which maintain the forward DNS data i e name to address mapping for that zone You will need one forward DDNS Domain for each zone you wish to service It may very well be that some or all of your zones are maintained by the same servers You will still need one DDNS Domain per zone Remember that matching a request to the appropriate server s is done by zone and a DDNS Domain only defines a single zone This section describes how to add Forward DDNS Domains Repeat these steps for each Forward DDNS Domain desired Each Forward DDNS Domain has the following parameters name The fully qualified domain name or zone that this DDNS Domain can update This is value used to compare against the request FQDN during forward matching It must be unique within the catalog key_name If TSIG
9. This subnet specifies the single option which will be included in the DHCPACK message to the client in response to DHCPIN FORM Note that the subnet definition does not require the address pool configuration 1f it will be used solely for the stateless configuration This server will associate the subnet with the client if one of the following conditions is met e The DHCPINFORM is relayed and the giaddr matches the configured subnet e The DHCPINFORM is unicast from the client and the ciaddr matches the configured subnet e The DHCPINFORM is unicast from the client the ciaddr is not set but the source address of the IP packet matches the configured subnet e The DHCPINFORM is not relayed and the IP address on the interface on which the message is received matches the configured subnet 7 2 13 Client Classification in DHCPv4 Note The DHCPv4 server has been extended to support limited client classification Although the current capability is modest it is expected to be expanded in the future However it is envisaged that the majority of client classification extensions will be using hooks extensions In certain cases it is useful to differentiate between different types of clients and treat them differently The process of doing classification is conducted in two steps The first step is to assess an incoming packet and assign it to zero or more classes This classification is currently simple but is expected to grow in capability s
10. ooa a 20 7 The DHCPv4 Server 21 7 1 Starting and Stopping the DHCPv4 Server ee 21 7 2 DHCPv4 Server Configuration 2 0 0 000022 ee 22 VA Introduchons e eci e we hal eS a a a a a eG ES 22 T22 Lease StOtage ri aa e e a ARR REG Dae aae E E e a eS Se E Se es 24 7 2 2 1 Memfile Basic Storage for Leases a 24 7 2 2 2 Database Configuration eR Rw ee eRe ee E 23 223 Interface contiguration lt e carse okie SS AE ts be 23 7 2 4 Issues with unicast responses to DHCPINFORM 2 0 000000 000004 27 T23 JPvA Subnet Identifier es A A a A A E ok 2 27 7 2 6 Configuration of IPv4 Address Pools oaaae 28 EZI Standard DACPV4 options x s pe cae e E Boke a ede a EA amp amp 29 7 2 8 Custom DHCPv4 options 31 7 2 9 DHCPv4 Vendor Specific Options 0 0 0002 2 ee 34 7 2 10 Nested DHCPv4 Options Custom Option Spaces 2 00 00 0000 eee 35 7 2 11 Unspecified parameters for DHCPv4 option configuration 37 7 2 12 Stateless Configuration of DHCPv4 clients 2 000 002 0000 000000 37 7 2 13 Client Classification in DHCPv4 naaa ee 38 7 2 13 1 Limiting Access to IPv4 Subnet to Certain Classes o 39 7 2 14 Configuring DHCPv4 for DDNS 2 000000 2 2 2 ee ee 39 7 2 14 1 DHCP DDNS Server Connectivity ooa a 40 Kea Administrator Reference Manual v 7 2 14 2 When Does the kea dhcp4 Server Gene
11. 1 is appended to the name if a 1 file exists it is renamed 2 etc If this is 0 no maximum file size is used Note Due to a limitation of the underlying logging library log4cplus rolling over the log files from 1 to 2 etc may show odd results There can be multiple small files at the timing of roll over This can happen when multiple processes try to roll over the files simultaneously Version 1 1 0 of log4cplus solved this problem so if this or higher version of log4cplus is used to build Kea it shouldn t happen Even for older versions it is normally expected to happen rarely unless the log messages are produced very frequently by multiple different processes 15 1 2 2 2 maxver integer Maximum number of old log files to keep around when rolling the output file Only relevant when output is file 15 1 3 Example Logger Configurations In this example we want to set the global logging to write to the console using standard output Mosela A loggers name kea dhcp4 UOUED ULwO PELOS ua VOUEPUELE EES Econ l severity WARN lt b gt In this second example we want to store debug log messages in a file that is at most 2MB and keep up to 8 copies of old logfiles Once the logfile grows to 2MB it will be renamed and a new file file be created Log g Enya loggers name kea dhcp6 NoUeEputtopeilons Lana output var log kea debug log
12. 2 DHCPRE QUEST 3 DHCPRELEASE 7 DHCPINFORM 8 DHCPACK 5 and DHCPNAK 6 DHCP Options and BOOTP Vendor Extensions RFC 2132 Supported options are PAD 0 END 255 Message Type 53 DHCP Server Identifier 54 Domain Name 15 DNS Servers 6 IP Address Lease Time 51 Subnet mask 1 and Routers 3 DHCP Relay Agent Information Option RFC 3046 Relay Agent Information option is supported Vendor Identifying Vendor Options for Dynamic Host Configuration Protocol version 4 RFC 3925 Vendor Identifying Vendor Class and Vendor Identifying Vendor Specific Information options are supported Client Identifier Option in DHCP Server Replies REC 6842 Server by default sends back client id option That capability may be disabled See Section 7 2 16 for details Kea Administrator Reference Manual 52 113 Statistic Data Type Description Number of DHCPv4 packets received This includes all packets valid a EBEN bogus corrupted rejected etc This statistic is expected to grow rapidly Number of DHCPDISCOVER packets received This statistic is expected to adkor inieper grow Its increase means that clients that just booted started their configuration process and their initial packets reached your server Number of DHCPOFFER packets received This statistic is expected to remain zero at all times as DHCPOFFER packets are sent by the server and the server is never expected pkt4 offer received integer to
13. 70E the qualifying suffix example com and the default value is used for generated prefix the generated FQDN would be myhost 3001 1 70E example com 8 3 Host reservation in DHCPv6 There are many cases where it is useful to provide a configuration on a per host basis The most obvious one is to reserve specific static IPv6 address or and prefix for exclusive use by a given client host returning client will get the same address or and prefix every time and other clients will never get that address Note that there may be cases when the new reservation has been made for the client for the address or prefix being currently in use by another client We call this situation a conflict The conflicts get resolved automatically over time as described in the subsequent sections Once conflict is resolved the client will keep receiving the reserved configuration when it renews Another example when the host reservations are applicable is when a host that has specific requirements e g a printer that needs additional DHCP options or a cable modem needs specific parameters Yet another possible use case for host reservation is to define unique names for hosts Although not all of the presented use cases are are implemented yet Kea software will support them in the near future Hosts reservations are defined as parameters for each subnet Each host can be identified by either DUID or its hardware MAC address See Section 8 8 for details There is
14. Consider the following series of events The server has configured the dynamic pool of addresses from the range of 192 0 2 10 to 192 0 2 20 The Host A requests an address and gets 19 0 2 10 Now the system administrator decides to reserve the address for the Host B He decides to reserve 192 0 2 10 for that purpose In general reserving an address that is currently assigned to someone else is not recommended but there are valid use cases where such an operation is warranted The server now has a conflict to resolve Let s analyze the situation here If the Host B boots up and requests an address the server is not able to assign the reserved address 192 0 2 10 for the Host B A naive approach would to be immediately remove the existing lease for the Host A and create a new one for the Host B That would not solve the problem though because as soon as the Host B gets the address it will detect that the address is already in use by the Host A and would send the DHCPDECLINE Kea Administrator Reference Manual 47 113 message Therefore in this situation the server has to temporarily assign a different address not matching what has been reserved to the Host B When the Host A renews its address the server will discover that the address being renewed is now reserved for another host the Host B Therefore the server will inform the Host A that it is no longer allowed to use it by sending DHCPNAK message The server will not remove the leas
15. We key_name dns_servers T Way selmsses TZ LS 1 30 Je Ci seres s 1172 12 30 f manene MILLO 00 DO O 0 26196 cas Y key_name dns_servers o arleesss YAO cias gau y gnamen O 192 anal cual Y key_name dns_servers pra daras S YILIZ 16 2 5 Y 9 3 DHCP DDNS Server Limitations The following are the current limitations of the DHCP DDNS Server e Requests received from the DHCP servers are placed in a queue until they are processed Currently all queued requests are lost when the server shuts down Kea Administrator Reference Manual 95 113 Chapter 10 The LFC process 10 1 Overview kea lfc is a service process that removes redundant infomation from the files used to provide persistent storage for the memfile data base backend This service is written to run as a stand alone process While kea Ife can be started externally there is usually no need to do this kea lfc is run on a periodic basis by the Kea DHCP servers The process operates on a set of files using them for input and output of the lease entries and to indicate where it is in the process in case of an interruption Currently the caller must supply names for all of the files in the future this requirement may be relaxed with the process getting the names from either the config file or from defaults 10 2 Command Line Options kea lfe is run as follows ESAS 4 6l ERE O il gt pier
16. are assumed The flag is convenient for temporarily switching the server into maximum verbosity e g when debugging y prints out Kea version and exits Kea Administrator Reference Manual 87 113 e V prints out Kea extended version with additional parameters and exits e W prints out Kea configuration report and exits The V command returns the versions of the external libraries dynamically linked The W command describes the environment used to build Kea This command displays a copy of the config report file produced by configure that is embedded in the executable binary The config report may also be accessed more directly The following command may be used to extract this information The binary path may be found in the install directory or in the 1ibs subdirectory in the source treee For example kea src bin d2 libs kea dhcp ddns strings path kea dhcp ddns sed n s p Upon start up the module will load its configuration and begin listening for NCRs based on that configuration During startup the server will attempt to create a PID file of the form localstatedir conf name kea dhcp ddns pid where e localstatedir The value as passed into the build configure script It defaults defaults to usr local var Note that this value may be overridden at run time by setting the environment variable KEA_PIDFILE_DIR This is intended primarily for testing purposes e conf name The confguration
17. data 12345 Kea Administrator Reference Manual 32 113 Returned if not Name Code Type Array requested time offset 2 int32 false false routers 3 ipv4 address true true time servers 4 ipv4 address true false name servers 5 ipv4 address true false domain name servers 6 ipv4 address true true log servers 7 ipv4 address true false cookie servers 8 ipv4 address true false lpr servers 9 ipv4 address true false impress servers 10 ipv4 address true false nad 11 ipv4 address true false servers boot size 13 uintl6 false false merit dump 14 string false false domain name 15 fqdn false true swap server 16 ipv4 address false false root path 17 string false false extensions path 18 string false false ip forwarding 19 boolean false false HON focal sence 20 boolean false false routing policy filter 21 ipv4 address true false reba ata 22 uintl6 false false reassembly default ip ttl 23 uint8 false false pal tacos 24 uint32 false false timeout path mate steal 25 uintl6 true false table interface mtu 26 uintl6 false false all subnets local 27 boolean false false broadcast address 28 ipv4 address false false P AS 29 boolean false false discovery mask supplier 30 boolean false false router discovery 31 boolean false false tantr SO NCIAnOO 32 ipv4 address false false address static routes 33 ipv4 addres
18. pools pool 192 0 2 10 192 0 2 20 1 Note that subnet is defined as a simple string but the pools parameter is actually a list of pools for this reason the pools definition is enclosed in square brackets even though only one range of addresses is specified in this example Each pool is a structure that contains the parameters that describe a single pool Currently there is only one parameter pool which gives the range of addresses in the pool Additional parameters will be added in future releases of Kea It is possible to define more than one pool in a subnet continuing the previous example further assume that 192 0 2 64 26 should be also be managed by the server It could be written as 192 0 2 64 to 192 0 2 127 Alternatively it can be expressed more simply as 192 0 2 64 26 Both formats are supported by Dhcp4 and can be mixed in the pool list For example one could define the following pools nacos Tf subnert4 veubi eea VUSZ 0 2 0 24 pools pool 192 0 2 10 192 0 2 20 Kea Administrator Reference Manual 29 113 pool 192 0 2 64 26 1 The number of pools is not limited but for performance reasons it is recommended to use as few as possible White space in pool definitions is ignored so spaces before and after the hyphen are optional They can be used to improve readability The server may be configured to serve more than one subnet Dhcp4 subnet4 Ema 3
19. this also requires that the particular option has its definition it is either a standard option or an administrator created a definition for the option using an option def structure as the option definition associates an option with a particular name It is possible to configure an option for which there is no definition unspecified option format Configuration of such options requires the use of option code e space if the option space is unspecified it will default to dhcp4 which is an option space holding DHCPv4 standard options e data if the option data is unspecified it defaults to an empty value The empty value is mostly used for the options which have no payload boolean options but it is legal to specify empty values for some options which carry variable length data and which spec allows for the length of 0 For such options the data parameter may be omitted in the configuration e csv format if this value is not specified and the definition for the particular option exists the server will assume that the option data is specified as a list of comma separated values to be assigned to individual fields of the DHCP option If the definition does not exist for this option the server will assume that the data parameter contains the option payload in the binary format represented as a string of hexadecimal digits Note that not specifying this parameter doesn t imply that it defaults to a fixed value but the configuration
20. 113 match client id true subnet4 1 Sta MSZ O 100 2480 ostia T it posi 192 0 2 23 19 606450 de dp match client id false tSuase 2s VLO 0 00 83 POSES O DOME OA ZE MO ORI lly The match client id is a boolean value which controls this behavior The default value of true indicates that the server will use the client identifier for lease lookups and chaddr if the first lookup returns no results The false means that the server will only use the chaddr to search for client s lease Whether the DHCID for DNS updates is generated from the client identifier or chaddr is controlled through the same parameter accordingly The match client id parameter may appear both in the global configuration scope and or under any subnet declaration In the example shown above the effective value of the match client id will be false for the subnet 192 0 10 0 24 because the subnet specific setting of the parameter overrides the global value of the parameter The effective value of the match client id for the subnet 10 0 0 0 8 will be set to true because the subnet declaration lacks this parameter and the global setting is by default used for this subnet In fact the global entry for this parameter could be omitted in this case because true is the default value It is important to explain what happens when the client obtains its lease for one setting of the match client id and then renews when the setting has bee
21. 31 113 The currently supported standard DHCPv4 options are listed in Table 7 1 and Table 7 2 The Name and Code are the values that should be used as a name in the option data structures Type designates the format of the data the meanings of the various types is given in Table 7 3 Some options are designated as arrays which means that more than one value is allowed in such an option For example the option time servers allows the specification of more than one IPv4 address so allowing clients to obtain the addresses of multiple NTP servers The Section 7 2 8 describes the configuration syntax to create custom option definitions formats It is generally not allowed to create custom definitions for standard options even if the definition being created matches the actual option format defined in the RFCs There is an exception from this rule for standard options for which Kea does not provide a definition yet In order to use such options a server administrator must create a definition as described in Section 7 2 8 in the dhcp4 option space This definition should match the option format described in the relevant RFC but the configuration mechanism will allow any option format as it has no means to validate the format at the moment 7 2 8 Custom DHCPv4 options Kea supports custom non standard DHCPv4 options Assume that we want to define a new DHCPv4 option called foo which will have code 222 and will convey a single unsigned 3
22. ARP communication and then sending the DHCP packet over the wire the DHCP server has no means to determine that the ARP exchange failed and the DHCP response message was dropped Thus the server does not log any error messages when the outgoing DHCP response is dropped At the same time all hooks pertaining to the packet sending operation will be called even though the message never reaches its destination Note that the issue described in this section is not observed when the raw sockets are in use because in this case the DHCP server builds all the layers of the outgoing message on its own and does not use ARP Instead it inserts the value carried in the chaddr field of the DHCPINFORM message into the link layer Server administrators willing to support DHCPINFORM messages via relays should not block ARP traffic in their networks or should use raw sockets instead of UDP sockets 7 2 5 IPv4 Subnet Identifier The subnet identifier is a unique number associated with a particular subnet In principle it is used to associate clients leases with their respective subnets When a subnet identifier is not specified for a subnet being configured it will be automatically assigned Kea Administrator Reference Manual 28 113 by the configuration mechanism The identifiers are assigned from 1 and are monotonically increased for each subsequent subnet 123 bees If there are multiple subnets configured with auto generated identifiers and
23. Hence Kea will fail to work on interfaces which use different data link layer header formats e g Infiniband The DHCPv4 server does not verify that assigned address is unused According to RFC 2131 the allocating server should verify that address is not used by sending ICMP echo request Address duplication report DECLINE is not supported yet The server doesn t act upon expired leases In particular when a lease expires the server doesn t request the removal of the DNS records associated with it Expired leases can be recycled Kea Administrator Reference Manual 54 113 Chapter 8 The DHCPv6 Server 8 1 Starting and Stopping the DHCPv6 Server It is recommended that the Kea DHCPv6 server be started and stopped using keactrl described in Chapter 6 However it is also possible to run the server directly it accepts the following command line switches C file specifies the configuration file This is the only mandatory switch d specifies whether the server logging should be switched to verbose mode In verbose mode the logging severity and debuglevel specified in the configuration file are ignored and debug severity and the maximum debuglevel 99 are assumed The flag is convenient for temporarily switching the server into maximum verbosity e g when debugging p port specifies UDP port on which the server will listen This is only useful during testing as a DHCPV6 server listening on ports other than
24. Kea homepage The details of keactrl script usage can be found in Chapter 6 2 2 Running Kea servers directly Kea servers can be started directly without a need to use keactrl To start DHCPv4 server run the following commmand kea dhcp4 c path to your kea4 config file json And to start the DHCPv6 server run the following command kea dhcp6 c path to your kea6 config file json Kea Administrator Reference Manual 5 113 Chapter 3 Installation 3 1 Packages Some operating systems or software package vendors may provide ready to use pre built software packages for Kea Installing a pre built package means you do not need to install build only prerequisites and do not need to make the software FreeBSD ports NetBSD pkgsrc and Debian testing package collections provide all the prerequisite packages 3 2 Install Hierarchy The following is the directory layout of the complete Kea installation all directories paths are relative to the installation direc tory etc kea configuration files include C development header files 1ib libraries sbin server software and commands used by the system administrator share kea configuration specifications and examples share doc kea this guide other supplementary documentation and examples share man manual pages online documentation var kea server identification lease databases and log files 3 3 Building
25. Manual 78 113 the reservation Similar as before the server will send two addresses the temporarily assigned one with zeroed lifetimes and the new one that matches reservation with proper lifetimes set This recovery will succeed even if other hosts will attempt to get the reserved address Had the host C requested address 2001 db8 10 after the reservation was made the server will propose a different address This recovery mechanism allows the server to fully recover from a case where reservations conflict with existing leases This procedure takes time and will roughly take as long as renew timer value specified The best way to avoid such recovery is to not define new reservations that conflict with existing leases Another recommendation is to use out of pool reservations If the reserved address does not belong to a pool there is no way that other clients could get this address note that having multiple reservations for the same address is not allowed 8 3 3 Reserving a hostname When the reservation for the client includes the hostname the server will assign this hostname to the client and send it back in the Client FQDN if the client sent the FQDN option to the the server The reserved hostname always takes precedence over the hostname supplied by the client via the FQDN option or the autogenerated from the IPv6 address hostname The server qualifies the reserved hostname with the value of the qualifying suffix parameter For
26. Manual 9 113 3 6 2 Building with PostgreSQL support Install PostgreSQL according to the instructions for your system The client development libraries must be installed Client development libraries are often packaged as libpq Build and install Kea as described in Chapter 3 with the following modification To enable the PostgreSQL database code at the configure step see Section 3 4 3 do configure other options with dhcp pgsql Or specify the location of the PostgreSQL configuration program pg_ config if PostgreSQL was not installed in the default location configure other options with dhcp pgsql path to pg_config See Section 4 3 3 1 for details regarding PostgreSQL database configuration Kea Administrator Reference Manual 10 113 Chapter 4 Kea Database Administration 4 1 Databases and Database Version Numbers Kea stores leases in one of several supported databases As future versions of Kea are released the structure of those databases will change For example Kea currently only stores lease information in the future additional data such as host reservation details will also be stored A given version of Kea expects a particular structure in the database It ensures this by checking the version of the database it is using Separate version numbers are maintained for backend databases independent of the version of Kea itself It is possible that the backend database version will stay th
27. Requirements In addition to the run time requirements listed in Section 1 2 building Kea from source code requires various development include headers and program development tools Note Some operating systems have split their distribution packages into a run time and a development package You will need to install the development package versions which include header files and libraries to build Kea from the source code Kea Administrator Reference Manual 6 113 Building from source code requires the following software installed on the system e Boost build time headers http www boost org At least Boost version 1 35 is required e Botan at least version 1 8 or OpenSSL e log4cplus at least version 1 0 3 development include headers e A C compiler and standard development headers Kea builds have been tested with GCC g 3 4 3 4 1 2 4 1 3 4 2 1 4 3 2 and 4 4 1 Clang 2 8 and Sun C 5 10 e The development tools make Visit the user contributed wiki at http kea isc org wiki SystemSpecificNotes for system specific installa tion tips 3 4 Installation from Source Kea is open source software written in C It is freely available in source code form from ISC as a downloadable tar file or via Kea Git code revision control service It may also be available in pre compiled ready to use packages from operating system vendors 3 4 1 Download Tar File The Kea release tarballs may be downloaded
28. Support for the development of the DHCPv4 DHCPv6 and DHCP DDNS components was provided by Comcast Kea was initially implemented as a collection of applications within the BIND 10 framework Hence Kea development would not be possible without the generous support of past BIND 10 project sponsors JPRS and CIRA were Patron Level BIND 10 sponsors AFNIC CNNIC CZ NIC DENIC eG Google RIPE NCC Registro br nz Registry Services and Technical Center of Internet were past BIND 10 sponsors Afilias IIS SE Nominet and SIDN were founding sponsors of the BIND 10 project
29. When diagnosing the problem with the server s operation it is often desired to use the DEBUG logging level to obtain the verbose output from the server and libraries it uses However high verbosity may be an overkill for the logging system in cases when the server is processing high volume traffic To mitigate this problem Kea is using multiple loggers which can be configured independently and which are responsible for logging messages from different functional parts of the server If the user trying to diagnose the problem has a reasonably high confidence that the problem origins in a specific function of the server or the problem is related to the specific type of operation he may enable high verbosity only for the relevant logger thus limiting the debug messages to the required minimum The loggers are associated with a particular library or binary of Kea However each library or binary may and usually does include multiple loggers For example the DHCPv4 server binary contains separate loggers for packet parsing for dropped packets for callouts etc Each logger derives its configuration from the root logger In the typical case the root logger configuration is the only logging configuration specified in the configuration file Creating a specific configuration for the selected logger thus overriding the configuration settings specified in the root logger configuration requires putting its configuration aside of the root logger s con
30. a single client to lease multiple addresses and multiple prefixes at the same time In the upcoming Kea releases it will be possible to have multiple addresses and prefixes reserved for a single host Therefore ip addresses and prefixes are plural and are actually arrays As of 0 9 1 having more than one IPv6 address or prefix is only partially supported Making a reservation for a mobile host that may visit multiple subnets requires a separate host definition in each subnet it is expected to visit It is not allowed to define multiple host definitions with the same hardware address in a single subnet It is a valid configuration if such definitions are specified in different subnets though The reservation for a given host should include only one identifier either DUID or hwardware address Defining both for the same host is considered a configuration error but as of 0 9 1 beta it is not rejected Adding host reservation incurs a performance penalty In principle when the server that does not support host reservation responds to a query it needs to check whether there is a lease for a given address being considered for allocation or renewal The server that also supports host reservation has to perform additional checks not only if the address is currently used if there is a lease for it but also whether the address could be used by someone else if there is a reservation for it That additional check incurs performance penalty 8 3 1 Addres
31. and 2001 db8 1 babe Mao Sif Hopretrons daran name dns servers code 23 space dhcp6 csv format false data 2001 ODB8 0001 0000 0000 0000 0000 CAFE 2001 0DB8 0001 0000 0000 0000 0000 BABE The value for the setting of the data element is split across two lines in this document for clarity when entering the command the whole string should be entered on the same line Care should be taken to use proper encoding when using hexadecimal format as Kea s ability to validate data correctness in hexadecimal is limited Most of the parameters in the option data structure are optional and can be omitted in some circumstances as discussed in the Section 8 2 12 Kea Administrator Reference Manual 63 113 It is possible to override options on a per subnet basis If clients connected to most of your subnets are expected to get the same values of a given option you should use global options you can then override specific values for a small number of subnets On the other hand if you use different values in each subnet it does not make sense to specify global option values Dhcp6 option data rather you should set only subnet specific values Dhcp6 subnet X option datal Y The following commands override the global DNS servers option for a particular subnet setting a single DNS server with address 2001 db8 1 3 Macas i subneto option data name dns servers code 23 space
32. be achieved in the following way UiDieiote 8 f subnet6 Subasta 0 01 Sea oA Meoollss Moelle 200 scales ZOOL acle IL 8 8 se araese Kea Administrator Reference Manual 72 113 r client class VENDOR_CLASS_eRouter1 0 Care should be taken with client classification as it is easy for clients that do not meet class criteria to be denied any service altogether 8 2 19 Configuring DHCPv6 for DDNS As mentioned earlier kea dhcp6 can be configured to generate requests to the DHCP DDNS server referred to here as D2 to update DNS entries These requests are known as NameChangeRequests or NCRs Each NCR contains the following informa tion 1 Whether it is a request to add update or remove DNS entries 2 Whether the change requests forward DNS updates AAAA records reverse DNS updates PTR records or both 3 The FQDN lease address and DHCID The parameters controlling the generation of NCRs for submission to D2 are contained in the dhcp ddns section of kea dhcp6 configuration The mandatory parameters for the DHCP DDNS configuration are enable updates which is unconditionally required and qualifying suffix which has no default value and is required when enable updates is set to true The two disabled and enabled minimal DHCP DDNS configurations are agas 1 Nglnxejo cleins e enable updates false r and for example Hipoveyoxey a af GING ceire Y 1 enable updates true qu
33. changes it may be impossible to subsequently downgrade to an earlier version To perform an upgrade issue the following command kea admin lease upgrade mysql u database user p database password n database name 4 3 3 PostgreSQL A PostgreSQL database must be set up if you want Kea to store lease and other information in PostgreSQL This step can be safely ignored if you are using other database backends 4 3 3 1 Manually Create the PostgreSQL Database and the Kea User The first task is to create both the lease database and the user under which the servers will access it A number of steps are required 1 Log into PostgreSQL as root sudo u postgres psql postgres Enter password postgres 2 Create the database postgres CREATE DATABASE database name CREATE DATABASE postgres dat abase name is the name you have chosen for the database 3 Create the user under which Kea will access the database and give it a password then grant it access to the database Kea Administrator Reference Manual 13 113 postgres CREATE USER user name WITH PASSWORD password CREATE ROLE postgres postgres GRANT ALL PRIVILEGES ON DATABASE database name TO user name GRANT postgres 4 Exit PostgreSQL postgres q Bye 5 At this point you are ready to create the database tables This can be done using the kea admin tool as explained in the next section recommende
34. data interpretation also depends on the presence of the option definition An administrator must be aware if the definition for the particular option exists when this parameter is not specified It is generally recommended to not specify this parameter only for the options for which the definition exists e g standard options Setting csv format to an explicit value will cause the server to strictly check the format of the option data specified 7 2 12 Stateless Configuration of DHCPv4 clients The DHCPv4 server supports the stateless client configuration whereby the client has an IP address configured e g using manual configuration and only contacts the server to obtain other configuration parameters e g DNS servers addresses In order to obtain the stateless configuration parameters the client sends the DHCPINFORM message to the server with the ciaddr set to Kea Administrator Reference Manual 38 113 the address that the client is currently using The server unicasts the DHCPACK message to the client that includes the stateless configuration yiaddr not set The server will respond to the DHCPINFORM when the client is associated with the particular subnet defined in the server s configuration The example subnet configuration will look like this once al subnet4 Epa s VILA 0 2 O 2a op Eno Scan A name domain name servers MEO eI 6 Maras 192022007 1920 2 201 csv format true space dhcp4
35. dhcp_ddns_srv parameters should be modified The kea_verbose parameter specifies the verbosity of the servers being started When kea_verboseis set to yes the logging level of the server is set to DEBUG Otherwise the default logging level is used Note The verbosity for the server is set when it is started Once started the verbosity can be only changed by stopping the server and starting it again with the new value of the kea_verbose parameter 6 4 Commands The following commands are supported by keactrl to perform specific operations on the Kea servers e start starts selected servers e stop stops all running servers e reload triggers reconfiguration of the selected servers by sending the SIGHUP signal to them e status returns the status of the servers active or inactive and the names of the configuration files in use Typical output from keactrl when starting the servers looks similar to the following keactrl start INFO keactrl Starting kea dhcp4 c usr local etc kea kea conf d INFO keactrl Starting kea dhcp6 c usr local etc kea kea conf d INFO keactrl Starting kea dhcp ddns c usr local etc kea kea conf d Kea s servers create PID files upon startup These files are used by keactrl to deteremine whether or not a given server is running If one or more servers are running when the start command is issued the output will look similiar to the following Kea Administrator Reference Manual 1
36. example the following subnet configuration subnet6 vsubne e YAO cos silos pais Moyooukstes 1 Mois V2 ole close s4804 t Tz reservations Volvio MOL SO ROS 3104 3 Oey svg 082 Ole SIO 10s Usiyo eolchaesses ls VANO coi ELO 1 hostname alice laptop r Welie AAN Sl enable updates true gqualifying suffix example isc org will result in assigning the alice laptop example isc org hostname to the client using the DUID 01 02 03 04 05 0A 0B 0C 0D 0E If the qualifying suffix is not specified the default empty value will be used and in this case the value specified as a hostname will be treated as fully qualified name Thus by leaving the qualifying suffix empty it is possible to qualify hostnames for the different clients with different domain names subnet6 mosca MANOS cl Sls e a oslsts E Pros ADS fw 3 il reservations Torio WOLSOASOS 9041093 WALCO O CR ODRO EE tipa dan es s Ss O Ole ON hostname mark desktop example org P Melacio ellasig 4 enable updates true will result in assigning the mark desktop example org hostname to the client using the DUID 01 02 03 04 05 0A 0B 0C 0D 0E Kea Administrator Reference Manual 79 113 8 3 4 Reserving specific options Currently it is not possible to specify options in host reservation Such a feature will be added in the upcoming Kea releases 8 3 5 Fine Tuning IPv6 Ho
37. example com 172 16 2 5 match The FQDN myhost four example com will match the first domain four example com while admin example com will match the third domain example com The FQDN other example net will fail to match any domain and would be rejected Table 9 2 Forward DDNS Domains Needed The following example configuration specified the Forward DDNS Domains UDhicpDdnisias Storward dos 1 duns do aias name four example com key_name Aa dns_servers olmo evelchasicyss 3 ip_ address ho SE MULAS y name six example com key_name Ae dns_servers ip_ address ho 20 siolovss sek name example com key_name A dns_servers ip_ address Yo lt b gt Similarly we need to construct the three reverse DDNS Domains An address of 192 0 2 150 will match the first domain ATT AGD DA oy 2001 db8 1 10 will match the second domain and 192 0 50 77 the third domain Kea Administrator Reference Manual 94 113 DDNS Domain Name DNS Servers 1 2 0 192 in addr arpa 172 16 1 5 172 16 2 5 2 1 0 0 0 8 d b 0 1 0 0 2 ip6 arpa 3001 1 50 3 0 182 in addr arpa 172 16 2 5 Table 9 3 Reverse DDNS Domains Needed These Reverse DDNS Domains are specified as follows UND aveyoibyokatss el reverse_ddns vidns domains Maeda WO AS oa oa cua
38. first Kea installation The database is initialized to the latest version supported by the version of the software lease version Reports the lease database version number This is not necessarily equal to the Kea version number as each backend has its own versioning scheme lease upgrade Conducts a lease database upgrade This is useful when upgrading Kea lease dump Dumps the contents of the lease database for MySQL or PostgreSQL backends to CSV text file The first line of the file contains the column names This is meant to be used as a diagnostic tool that provides a portable human readable form of lease data backend specifies the backend type Currently supported types are Kea Administrator Reference Manual 11 113 e memfile Lease information is stored on disk in a text file e mysql Lease information is stored in a MySQL relational database e pgsql Lease information is stored in a PostgreSQL relational database Additional parameters may be needed depending on your setup and specific operation username password and database name or the directory where specific files are located See appropriate manual page for details man 8 kea admin 4 3 Supported Databases 4 3 1 memfile There are no special initialization steps necessary for the memfile backend During the first run both kea dhcp4 and kea dhcp6 will create an empty lease file if one is not present Necessary disk write permission is req
39. if several processes log to the same file KEA_LOGGER_DESTINATION Specifies logging output There are several special values stdout Log to standard output stderr Log to standard error syslog fac Log via syslog The optional fac which is separated from the word syslog by a colon specifies the facility to be used for the log messages Unless specified messages will be logged using the facility local0 Any other value is treated as a name of the output file If not specified otherwise Kea will log to standard output Kea Administrator Reference Manual 111 113 Chapter 16 Frequently Asked Questions This chapter contains a number of frequently asked questions and troubleshooting tips It currently lacks content but it is expected to grow over time 16 1 Generic Frequently Asked Questions 16 1 1 Where did the Kea name came from Kea is the name of a high mountain parrot living in New Zealand See this https lists isc org pipermail kea users 2014 October 000032 html for an extended answer 16 1 2 Feature X is not supported yet When if will it be available Kea is developed by a small team of engineers Our resources are limited so we need to prioritize requests The complexity of a new feature how difficult it is to implement a feature and how likely it would break something that already works amount of work required and expected popularity 1 e how many users would actually benefit from it are three
40. in deployments where the server receives only relayed traffic These benefits are mentioned in the Section 7 2 3 From the administrator s perspective it is often desired to be able to configure the system s firewall to filter out the unwanted traffic and the use of UDP sockets faciliates it However the administrator must also be aware of the implications related to filtering certain types of traffic as it may impair the DHCP server s operation In this section we are focusing on the case when the server receives the DHCPINFORM message from the client via a relay According to the RFC 2131 the server should unicast the DHCPACK response to the address carried in the ciaddr field When the UDP socket is in use the DHCP server relies on the low level functions of an operating system to build the data link IP and UDP layers of the outgoing message Typically the OS will first use ARP to obtain the client s link layer address to be inserted into the frame s header if the address is not cached from a previous transaction that the client had with the server When the ARP exchange is successful the DHCP message can be unicast to the client using the obtained address Some system administrators block ARP messages in their network which causes issues for the server when it responds to the DHCPINFORM messages because the server is unable to send the DHCPACK if the preceding ARP communication fails Since the OS is entirely responsible for the
41. in the Dhcp6 component can be referred to as Dhcp6 valid lifetime and the pool in the first subnet defined in the DHCPv6 configuration as Dhcp6 subnet6 0 pool Kea Administrator Reference Manual 17 113 Chapter 6 Managing Kea with keactrl 6 1 Overview keactrl is a shell script which controls the startup shutdown and reconfiguration of the Kea servers kea dhcp4 kea dhcp6 and kea dhcp ddns It also provides the means for checking the current status of the servers and determining the configuration files in use 6 2 Command Line Options keactrl is run as follows keactrl lt command gt c keactrl config file s server server lt command gt is the one of the commands described in Section 6 4 The optional c keactrl config file switch allows specification of an alternate keactrl configuration file ctrl config is a synonym for c In the absence of c keactrl will use the default configuration file kea install dir etc kea keactrl conf The optional s server server switch selects the servers to which the command is issued server is a synonym for s If absent the command is sent to all servers enabled in the keactrl configuration file If multiple servers are specified they should be separated by commas with no intervening spaces 6 3 The keactrl Configuration File Depending on requirements not all of the available servers need be run The keactrl configuration file sets which server
42. indicating success and the specified statistic as the value of arguments parameter If the requested statistic is not found the response will contain an empty map i e only as argument but the status code will still be set to success 0 12 3 2 statistic reset command statistic reset command sets the specified statistic to its neutral value 0 for integer 0 0 for float OhOmOsOus for time duration and for string type It takes a single string parameter called name that specifies the statistic name An example command may look like this command statistic reset arguments name pkt4 received If the specific statistic is found and reset was successful the server will respond with a status of 0 indicating success and an empty parameters field If an error is encountered e g requested statistic was not found the server will return a status code of 1 error and the text field will contain the error description 12 3 3 statistic remove command statistic remove command attempts to delete a single statistic It takes a single string parameter called name that specifies the statistic name An example command may look like this Kea Administrator Reference Manual 100 113 command statistic remove arguments name pkt4 received If the specific statistic is found and its removal was successful the server will respond with a status of 0 indicating success and an empty parameters field If
43. interface For example the server that is intended to serve a local subnet over ethO may be configured as follows Macao if subnet6 subnet 2001 db8 beef 48 Moools 3 i POSI O Os besre aie le interface eth0 8 2 14 Rapid Commit The Rapid Commit option described in RFC 3315 is supported by the Kea DHCPv6 server However support is disabled by default for all subnets It can be enabled for a particular subnet using the rapid commit parameter as shown below Deeg if subnetoe Subasta 2001 ds beer n 4c rapid commit true MEROS pool 200M dos besit 12001 dbsisbeek son l Kea Administrator Reference Manual 70 113 This setting only affects the subnet for which the rapid commit is set to true For clients connected to other subnets the server will ignore the Rapid Commit option sent by the client and will follow the 4 way exchange procedure i e respond with the Advertise for the Solicit containing Rapid Commit option 8 2 15 DHCPv6 Relays A DHCPVv6 server with multiple subnets defined must select the appropriate subnet when it receives a request from a client For clients connected via relays two mechanisms are used The first uses the linkaddr field in the RELAY_FORW message The name of this field is somewhat misleading in that it does not contain a link layer address instead it holds an address typically a global address that is used to identify a link The DHCPv6
44. interface connected to the link on which the clients are being configured Typically the relay has an IPv4 address configured on that interface that belongs to the subnet from which the server will assign addresses In the typical case the server is able to use the IPv4 address inserted by the relay in the giaddr field of the DHCPv4 packet to select the appropriate subnet However that is not always the case In certain uncommon valid deployments the relay address may not match the subnet This usually means that there is more than one subnet allocated for a given link The two most common examples where this is Kea Administrator Reference Manual 50 113 the case are long lasting network renumbering where both old and new address space is still being used and a cable network In a cable network both cable modems and the devices behind them are physically connected to the same link yet they use distinct addressing In such a case the DHCPv4 server needs additional information the IPv4 address of the relay to properly select an appropriate subnet The following example assumes that there is a subnet 192 0 2 0 24 that is accessible via a relay that uses 10 0 0 1 as its IPv4 address The server will be able to select this subnet for any incoming packets that came from a relay that has an address in 192 0 2 0 24 subnet It will also select that subnet for a relay with address 10 0 0 1 Dhcp4 subnet4 STONE ts Wile 047
45. interface yet This requires that the server injects the hardware address of the destination into the data link layer of the packet being sent to the client The DHCPv4 server utilizes the raw sockets to achieve this and builds the entire IP UDP stack for the outgoing packets The down side of raw socket use however is that incoming and outgoing packets bypass the firewalls e g iptables It is also troublesome to handle traffic on multiple IPv4 addresses assigned to the same interface as raw sockets are bound to the interface and advanced packet filtering techniques e g using the BPF have to be used to receive unicast traffic on the desired addresses assigned to the interface rather than capturing whole traffic reaching the interface to which the raw socket is bound Therefore in the deployments where the server doesn t have to provision the directly connected clients and only receives the unicast packets from the relay agents it is desired to configure the DHCP server to utilize the IP UDP datagram sockets instead of raw sockets The following configuration demonstrates how this can be achieved Kea Administrator Reference Manual 27 113 Ms Al interfaces config imeecrracess Us Techin Wess 1 dhcp socket type udp The dhcp socket type specifies that the IP UDP sockets will be opened on all interfaces on which the server listens i e eth and eth3 in our case If the dhcp socket type is set to raw it configure
46. is stored in the SQL database for each lease as a timestamp value Kea developers observed that MySQL database doesn t accept timestamps beyond 2147483647 seconds maximum signed 32 bit number from the beginning of the epoch At the same time some versions of PostgreSQL do accept greater values but the value is altered when it is read back For this reason the lease database backends put the restriction for the maximum timestamp to be stored in the database which is equal to the maximum signed 32 bit number This effectively means that the current Kea version can t store the leases which expiration time is later than 2147483647 seconds since the beginning of the epoch around year 2038 Kea Administrator Reference Manual 15 113 Chapter 5 Kea configuration Kea is designed to allow different methods by which it can be configured each method being implemented by a component known as a configuration backend At present only one such backend is available that allowing configuration by means of a JSON file 5 1 JSON configuration backend JSON is the default configuration backend It assumes that the servers are started from the command line either directly or using a script e g keactrl The JSON backend uses certain signals to influence Kea The configuration file is specified upon startup using the c parameter 5 1 1 JSON syntax Configuration files for DHCPv4 DHCPv6 and DDNS modules are defined in an extended JSON format Ba
47. is used with this domain s servers this value should be the name of the key from within the TSIG Key List to use If the value is blank the default TSIG will not be used in DDNS conversations with this domain s servers dns_servers A list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain The servers are used in a first to last preference In other words when D2 begins to process a request for this domain it will pick the first server in this list and attempt to communicate with it If that attempt fails it will move to next one in the list and so on until the it achieves success or the list is exhausted To create a new forward DDNS Domain one must add a new domain element and set its parameters WDnciobKckas 3 4 torwaro dans 3 dadas domains 1 name other example com key name dns_servers It is permissible to add a domain without any servers If that domain should be matched to a request however the request will fail In order to make the domain useful though we must add at least one DNS server to it 9 2 3 1 1 Adding Forward DNS Servers This section describes how to add DNS servers to a Forward DDNS Domain Repeat them for as many servers as desired for a each domain Forward DNS Server entries represent actual DNS servers which support the server side of the DDNS protocol Each Forward DNS Server has the following parameters e hostname
48. leading factors We sometimes also have contractual obligations Simply stating that you d like feature X is useful We try to implement features that are actively requested first but the reality is that we have more requests than we can handle so some of them must be postponed at least in the near future So is your request likely to be rejected Not at all You can do many things to greatly improve the chances of your request being fulfilled First 1t helps to explain why you need a feature If your explanation is reasonable and there are likely other users that would benefit from it the chances for Kea developers to put this task on a roadmap is better Saying that you are willing to participate in tests e g test engineering drops when they become available is also helpful Another thing you can do to greatly improve the chances of a feature to appear is to actually develop it on your own and submit a patch That s an avenue that people often forget about Kea is open source software and we do accept patches There are certain requirements like code quality comments unit tests documentation etc but we have accepted a significant number of patches in the past so it s doable Accepted contributions range from minor documentation corrections to significant new features like support for a new database type Before considering writing and submitting a patch make sure you read the Contributor s Guide in Kea Developer s Guide Kea is de
49. maxver 8 Kea Administrator Reference Manual 109 113 maxsize 204800 destinaron Weal Ie E severity DEBUG debuglevel 99 lt b gt 15 2 Logging Message Format Each message written to the configured logging destinations comprises a number of components that identify the origin of the message and if the message indicates a problem information about the problem that may be useful in fixing it Consider the message below logged to a file 2014 04 11 12 58 01 005 INFO kea dhcp4 dhcpsrv 27456 DHCPSRV_MEMFILE_DB opening memory file lease database type memfile universe 4 Note the layout of messages written to the system logging file syslog may be slightly different This message has been split across two lines here for display reasons in the logging file it will appear on one line The log message comprises a number of components 2014 04 11 12 58 01 005 The date and time at which the message was generated INFO The severity of the message kea dhcp4 dhcpsrv 27456 The source of the message This comprises two elements the Kea process generating the message in this case kea dhcp4 and the component within the program from which the message originated which is the name of the common library used by DHCP server implementations The number after the slash is a process id pid DHCPSRV_MEMFILE_DB The message identification Every message in Kea has a unique identification
50. pkt6 solicit received integer pkt6 advertise received integer pkt6 reply received integer Kea Administrator Reference Manual 85 113 IPv6 Prefix Options for Dynamic Host Configuration Protocol DHCP version 6 RFC 3633 Supported options are IA_PD and JA_PREFIX Also supported is the status code NoPrefixAvail DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 DHCPv6 RFC 3646 Supported option is DNS_SERVERS The Dynamic Host Configuration Protocol for IPv6 DHCPv6 Relay Agent Remote ID Option RFC 4649 REMOTE ID option is supported The Dynamic Host Configuration Protocol for IPv6 DHCPv6 Client Fully Qualified Domain Name FQDN Option RFC 4704 Supported option is CLIENT_FQDN Relay Supplied DHCP Options RFC 6422 Full functionality is supported OPTION_RSOO ability of the server to echo back the options checks whether an option is RSOO enabled ability to mark additional options as RSOO enabled Client Link Layer Address Option in DHCPv6 RFC 6939 Supported option is client link layer address option 8 12 DHCPv6 Server Limitations These are the current limitations and known problems with the DHCPv6 server software Most of them are reflections of the early stage of development and should be treated as not implemented yet rather than actual limitations On line configuration has some limitations Adding new subnets or modifying existing ones work as is rem
51. see Section 7 6 and Section 8 9 respectively To extract data from the statistics module the control channel can be used See Chapter 13 for details It is possible to retrieve a single or all statistics reset statistics i e set to neutral value typically zero or even remove completely a single or all statistics See section Section 12 3 for a list of statistic oriented commands 12 2 Statistics Lifecycle It is useful to understand how the Statistics Manager module works When the server starts operation the manager is empty and does not have any statistics When statistic get all is executed an empty list is returned Once the server performs an operation that causes a statistic to change the related statistic will be created In the general case once a statistic is recorded even once it is kept in the manager until explicitly removed by statistic remove or statistic remove all being called or the server is shut down Per subnet statistics are explicitly removed when reconfiguration takes place Statistics are considered run time properties so they are not retained after server restart Removing a statistic that is updated frequently makes little sense as it will be re added when the server code next records that statistic The statistic remove and statistic remove all commands are intended to remove statistics that are not expected to be Kea Administrator Reference Manual 99 113 observed in the near future For example a mi
52. sending a response Such messages include the information about the source and destination IP addresses and interfaces used to transmit packets This logger is also used to log messages related to subnet selection as this selection is usually based on the IP addresses and or interface names which can be retrieved from the received packet even before the DHCPv6 message carried in the packet is parsed kea dhcp ddns this is the root logger for the kea dhcp ddns deamon All components used by this deamon inherit the settings from this logger if there is no specialized logger provided kea dhcp ddns dhcpddns this is the logger used by the kea dhcp ddns deamon for logging configuration and global event information This logger does not specify logging settings for libraries used by the deamon kea dhcp ddns dhcp to d2 this is the logger used by the kea dhcp ddns deamon for logging information about events dealing with receving messages from the DHCP servers and adding them to the queue for processing kea dhcp ddns d2 to dns this is the logger used by the kea dhcp ddns deamon for logging information about events dealing with sending and receiving messages with the DNS servers Note that user defined hook libraries should not use any of those loggers and should define new loggers with names that corre spond to the libraries using them Suppose that the user created the library called libpacket capture to dump packets received and transmit
53. servers support statistics gathering since 0 9 2 beta version A working DHCP server encounters various events that can cause certain statistics to be collected For example a DHCPv4 server may receive a packet pkt4 received statistic increases by one that after parsing was identifier aa DHCPDISCOVER pkt4 discover received The Server processed it and decided to send DHCPOFFER representing its answer pkt4 offer sent and pkt4 sent statistics increase by one Such events happen frequently so 1t is not uncommon for the statistics to have values in high thousands They can serve as an easy and powerful tool for observing a server s and network s health For example if pkt4 received statistic stops growing it means that the clients packets are not reaching the server There are four types of statistics e integer this is the most common type It is implemented as 64 bit integer int64_t in C so it can hold any value between 2 63 to 2 63 1 e floating point this type is intended to store floating point precision It is implemented as double C type e duration this type is intended for recording time periods It uses boost posix_time time_duration type which stores hours minutes seconds and microseconds e string this type is intended for recording statistics in textual form It uses std string C type During normal operation DHCPv4 and DHCPV6 servers gather statistics For a list of DHCPv4 and DHCPV6 statistics
54. standard options it is possible to use their names rather than option code e g e g use dns servers instead of 23 See Table 8 1 for the names In certain cases it could also work for custom options but due to the nature of the parser code this may be unreliable and should be avoided 8 2 17 Client Classification in DHCPv6 Note DHCPV6 server has been extended to support limited client classification Although the current capability is modest it is expected to be expanded in the future It is envisaged that the majority of client classification extensions will be using hooks extensions In certain cases it is useful to differentiate between different types of clients and treat them differently The process of doing classification is conducted in two steps The first step is to assess an incoming packet and assign it to zero or more classes This classification is currently simple but is expected to grow in capability soon Currently the server checks whether the incoming packet includes vendor class option 16 If it has the content of that option is prepended with VENDOR_CLASS_ then it is interpreted as a class For example modern cable modems will send this option with value docsis3 0 and as a result the packet will belong to class VENDOR_CLASS_docsis3 0 It is envisaged that the client classification will be used for changing behavior of almost any part of the DHCP engine processing including assigning leases from different
55. the client using the MAC address aa bb cc dd ee ff If the qualifying suffix is not specified the default empty value will be used and in this case the value specified as a hostname will be treated as fully qualified name Thus by leaving the qualifying suffix empty it is possible to qualify hostnames for the different clients with different domain names Ksubnecams 1d stilo Hs WIO 0 0 0 24W Kea Administrator Reference Manual 48 113 Woolies f Moss 10 00 109 10 0 0 100 1 reservations hw address aa bb cc dd ee ff hostname alice laptop isc org hweacdress Le sare ose 39 25 hostname mark desktop example org 1 WolnG p Clin seme enable updates true 7 3 4 Reserving specific options Currently it is not possible to specify options in host reservation Such a feature will be added in the upcoming Kea releases 7 3 5 Fine Tuning IPv4 Host Reservation Note reservation mode configuration parameter in DHCPv4 server is accepted but not used in the Kea 0 9 2 Full implementation will be available in the upcoming releases Host reservation capability introduces additional restrictions for the allocation engine during lease selection and renewal In particular three major checks are necessary First when selecting a new lease it is not sufficient for a candidate lease to be not used by another DHCP client It also must not be reserved for another client Second
56. this subnet unless the id parameter is removed or set to 0 The value of 0 forces auto generation of the subnet identifier Kea Administrator Reference Manual 60 113 8 2 5 Unicast traffic support When the DHCPV6 server starts by default it listens to the DHCP traffic sent to multicast address ff02 1 2 on each interface that it is configured to listen on see Section 8 2 3 In some cases it is useful to configure a server to handle incoming traffic sent to the global unicast addresses as well The most common reason for that is to have relays send their traffic to the server directly To configure the server to listen on a specific unicast address the notation to specify interfaces has been extended An interface name can be optionally followed by a slash followed by the global unicast address on which the server should listen This will be done in addition to normal link local binding listening on ff02 1 2 address The sample configuration below shows how to listen on 2001 db8 1 a global address configured on the eth interface Tipe i interfaces config interfaces eth1 2001 db8 1 This configuration will cause the server to listen on eth on link local address multicast group ff02 1 2 and 2001 db8 1 It is possible to mix interface names wildcards and interface name addresses on the list of interfaces It is not possible to specify more than one unicast address on a given interface Care should be t
57. to log messages related to processing of the options in the DHCPv4 messages i e parsing options encoding options into on wire format and packet classification using options contained in the received packets Kea Administrator Reference Manual 106 113 kea dhcp4 packets this logger is mostly used to log messages related to transmission of the DHCPv4 packets i e packet reception and sending a response Such messages include the information about the source and destination IP addresses and interfaces used to transmit packets This logger is also used to log messages related to subnet selection as this selection is usually based on the IP addresses and or interface names which can be retrieved from the received packet even before the DHCPv4 message carried in the packet is parsed kea dhcp6 this is the root logger for the DHCPv6 server All components used by the DHCPv6 server inherit the settings from this logger if there is no specialized logger provided kea dhcp6 bad packets this is the logger used by the DHCPv6 server deamon for logging inbound client packets that were dropped kea dhcp6 callouts this logger is used to log messages pertaining to the callouts registration and execution for the particular hook point kea dhcp6 ddns this logger is used by the DHCPv6 server to log messages related to the Client FQDN option processing It also includes log messages related to the relevant DNS updates kea dhcp6 dhcp6 this i
58. which is the default backend MySQL and PostgreSQL 8 2 2 1 Memfile Basic Storage for Leases The server is able to store lease data in different repositories Larger deployments may elect to store leases in a database Section 8 2 2 2 describes this option In typical smaller deployments though the server will use a CSV file rather than a database to store lease information As well as requiring less administration an advantage of using a file for storage is that it eliminates a dependency on third party database software The configuration of the file backend Memfile is controlled through the Dhcp6 lease database parameters The type parameter is mandatory and it specifies which storage for leases the server should use The value of memfile indicates that the file should be used as the storage The following list presents the remaining not mandatory parameters which can be used to configure the Memfile backend e persist controls whether the new leases and updates to existing leases are written to the file It is strongly recommended that the value of this parameter is set to true at all times during the server s normal operation Not writing leases to disk will mean that if a server is restarted e g after a power failure it will not know what addresses have been assigned As a result it may hand out addresses to new clients that are already in use The value of false is mostly useful for performance testing purposes The default val
59. 0 24 loose Ys f pools 192 0 210 192 0 2 20Y 16 relay ip address 10 0 0 1 7 5 2 Segregating IPv4 Clients in a Cable Network In certain cases it is useful to mix relay address information introduced in Section 7 5 1 with client classification explained in Section 7 2 13 1 One specific example is cable network where typically modems get addresses from a different subnet than all devices connected behind them Let s assume that there is one CMTS Cable Modem Termination System with one CM MAC a physical link that modems are connected to We want the modems to get addresses from the 10 1 1 0 24 subnet while everything connected behind modems should get addresses from another subnet 192 0 2 0 24 The CMTS that acts as a relay uses address 10 1 1 1 The following configuration can serve that configuration Ms Al subnet4 Sumo VLO T 10 2407 Uocolet LETAL wio ot I2 10 11 20 1 client class docsis3 0 relay ip address 10 1 1 1 Ia eros OOR 2A Woxoolave M A poolses 192 0 2 10 T92 Mo 2 204 I relay ip address 10 1 1 1 Kea Administrator Reference Manual 51 113 7 6 Statistics in DHCPv4 server Note This section describes DHCPv4 specific statistics For a general overview and usage of statistics see Chapter 12 The DHCPv4 server supports the following statistics 7 7 Management API for the DHCPv4 server Management API has been intro
60. 2 bit integer value We can define such an option by using the following entry in the configuration file Ms Al option def name S foo 0 code 222 type uint32 array false record types space dhcp4 encapsulate The false value of the array parameter determines that the option does NOT comprise an array of uint32 values but rather a single value Two other parameters have been left blank record types and encapsulate The former specifies the comma separated list of option data fields if the option comprises a record of data fields This should be non empty if the type is set to record Otherwise it must be left blank The latter parameter specifies the name of the option space being encapsulated by the particular option If the particular option does not encapsulate any option space it should be left blank Note that the above set of comments define the format of the new option and do not set its values Note In the current release the default values are not propagated to the parser when the new configuration is being set Therefore all parameters must be specified at all times even if their values are left blank Once the new option format is defined its value is set in the same way as for a standard option For example the following commands set a global value that applies to all subnets Dhcp4 Toptien daros name foo code 222 space dhcp4 csv format true
61. 24 113 7 2 2 Lease Storage All leases issued by the server are stored in the lease database Currently there are three database backends available memfile which is the default backend MySQL and PostgreSQL 7 2 2 1 Memfile Basic Storage for Leases The server is able to store lease data in different repositories Larger deployments may elect to store leases in a database Section 7 2 2 2 describes this option In typical smaller deployments though the server will use a CSV file rather than a database to store lease information As well as requiring less administration an advantage of using a file for storage is that 1t eliminates a dependency on third party database software The configuration of the file backend Memfile is controlled through the Dhcp4 lease database parameters The type parameter is mandatory and it specifies which storage for leases the server should use The value of memfile indicates that the file should be used as the storage The following list presents the remaining not mandatory parameters which can be used to configure the Memfile backend e persist controls whether the new leases and updates to existing leases are written to the file It is strongly recommended that the value of this parameter is set to true at all times during the server s normal operation Not writing leases to disk will mean that if a server is restarted e g after a power failure it will not know what addresses have been assigned
62. 3 output_options list Each logger can have zero or more output_options These specify where log messages are sent These are explained in detail below The other options for a logger are 15 1 1 4 debuglevel integer When a logger s severity is set to DEBUG this value specifies what debug messages should be printed It ranges from 0 least verbose to 99 most verbose If severity for the logger is not DEBUG this value is ignored 15 1 2 Output Options The main settings for an output option are the dest ination and a value called output the meaning of which depends on the destination that is set 15 1 2 1 destination string The destination is the type of output It can be one of console e file e syslog Kea Administrator Reference Manual 108 113 15 1 2 2 output string This value determines the type of output There are several special values allowed here stdout messages are printed on standard output stderr messages are printed on stderr syslog messages are logged to syslog using default name syslog name messages are logged to syslog using specified name Any other value is interpreted as a filename that the logs should be written to The other options for output_options are 15 1 2 2 1 maxsize integer Only relevant when destination is file this is maximum file size of output files in bytes When the maximum size is reached the file is renamed and a new file opened For example a
63. 491 This vendor option is extracted from the original client s message not from any relay options 8 9 Statistics in DHCPv6 server Note This section describes DHCPv6 specific statistics For a general overview and usage of statistics see Chapter 12 The DHCPVv6 server supports the following statistics 8 10 Management API for the DHCPv6 server Management API has been introduced in Kea 0 9 2 beta It allows issuing specific management commands like statistics re trieval reconfiguration or shutdown For more details see Chapter 13 Currently the only supported communication channel type is UNIX stream socket By default there are no sockets open To instruct Kea to open a socket the following entry in the configuration file can be used UDNES Control socket gt Y socket type unix socket name path to the unix socket Ie subneto l The length of the path specified by the socket name parameter is restricted by the maximum length for the unix socket name on your operating system i e the size of the sun_path field in the sockaddr_un structure decreased by 1 This value varies on different operating systems between 91 and 107 characters The typical values are 107 on Linux and 103 on FreeBSD Communication over control channel is conducted using JSON structures See the Control Channel section in the Kea Developer s Guide for more details DHCPv6 server supports statistic get statistic reset statis
64. 9 113 keactrl start INFO keactrl kea dhcp4 appears to be running see PID 10918 PID file usr local var kea kea kea dhcp4 pid INFO keactrl kea dhcp6 appears to be running see PID 10924 PID file usr local var kea kea kea dhcp6 pid INFO keactrl kea dhcp ddns appears to be running see PID 10930 PID file usr local var kea kea kea dhcp ddns pid During normal shutdowns these PID files are deleted They may however be left over as remnants following a system crash It 1s possible though highly unlikely that upon system restart the PIDs they contain actually refer to processes unrelated to Kea This condition will cause keactrl to decide that the servers are running when in fact they are not In such a case the PID files as listed in the keactrl output must be manually deleted The following command stops all servers keactrl stop INFO keactrl Stopping kea dhcp4 INFO keactrl Stopping kea dhcp6 INFO keactrl Stopping kea dhcp ddns Note that the stop will attempt to stop all servers regardless of whether they are enabled in the keactrl conf If any of the servers are not running an informational message is displayed as in the stop command output below keactrl stop INFO keactrl kea dhcp4 isn t running INFO keactrl kea dhcp6 isn t running INFO keactrl kea dhcp ddns isn t running As already mentioned the reconfiguration of each Kea server is triggered by the SIGHUP signal Th
65. As a result 1t may hand out addresses to new clients that are already in use The value of false is mostly useful for performance testing purposes The default value of the persist parameter is true which enables writing lease updates to the lease file e name specifies an absolute location of the lease file in which new leases and lease updates will be recorded The default value for this parameter is kea install dir var kea kea leases4 csv e Ifc interval specifies the interval in seconds at which the server Memfile backend will perform a lease file cleanup LFC which removes the redundant historical information from the lease file and effectively reduces the lease file size The cleanup process is described in more detailed fashion further in this section The default value of the Ife interval is 0 which disables the LFC The example configuration of the Memfile backend is presented below Moacoa us lease database type memfile persist true name tmp kea leases4 csv lfc interval 1800 This configuration selects the tmp kea leases4 csv as the storage for lease information and enables persistence writing lease updates to this file It also configures the backend perform the periodic cleanup of the lease files executed every 30 minutes It is important to know how the lease file contents are organized to understand why the periodic lease file cleanup is needed Every time when the server updates a lea
66. C 2132 The RFC 2131 indicates that the server may use both of these identifiers to identify the client but the client identifier if present takes precedence over chaddr One of the reasons for this is that client identifier is independent from the hardware used by the client to communicate with the server For example if the client obtained the lease using one network card and then the network card is moved to another host the server will wrongly identify this host is the one which has obtained the lease Moreover the RFC 4361 gives the recommendation to use DUID see DHCPv6 specification carried as client identifier when dual stack networks are in use to provide consistent identification information of the client regardless of the protocol type it is using Kea adheres to these specifications and the client identifier by default takes precedence over the value carried in chaddr field when the server searches creates updates or removes the client s lease When the server receives a DHCPDISCOVER or DHCPREQUEST message from the client it will try to find out if the client already has a lease in the database and will hand out the existing lease rather than allocate a new one Each lease in the lease database is associated with the client identifier and or chaddr The server will first use the client identifer if present to search the lease If the lease is found the server will treat this lease as belongi
67. DHCPv4 configuration starts in this line aos First we set up global values valid lifetime 4000 renew timer 1000 tcebindstimer o 20005 Next we setup the interfaces to be used by the server interfaces config interfaces eth0 And we specify the type of lease database lease database type memfile persist true name var kea dhcp4 leases Finally we list the subnets from which we will be leasing addresses subuet1 s if sul me O OA Wroyeyodlai s E Msxexolls 192 021 192 0 2 200 DHCPv4 configuration ends with this line The following paragraphs provide a brief overview of the parameters in the above example and their format Subsequent sections of this chapter go into much greater detail for these and other parameters The lines starting with a hash are comments and are ignored by the server they do not impact its operation in any way The configuration starts in the first line with the initial opening curly bracket or brace Each configuration consists of one or more objects In this specific example we have only one object called Dhcp4 This is a simplified configuration as usually there will be additional objects like Logging or DhcpDns but we omit them now for clarity The Dhcp4 configuration starts with Kea Administrator Reference Manual 23 113 the Dhcp4 line and ends with the corresponding closing brace in the above example the bra
68. DNS server It receives name update requests from the DHCP servers and sends DNS Update messages to the DNS servers kea admin A tool useful for database backend maintenance creating new database checking versions upgrading etc kea lfc This process removes redundant information from the files used to provide persistent storage for the memfile data base backend The service is written to run as a stand alone process While it can be started externally it should be started by the Kea DHCP servers perfdhcp DHCP benchmarking tool which simulates multiple clients to test both DHCPv4 and DHCPv6 servers perfor mance The tools and modules are covered in full detail in this guide In addition manual pages are also provided in the default installation Kea also provides C libraries and programmer interfaces for DHCP These include detailed developer documentation and code examples Kea Administrator Reference Manual 3 113 Chapter 2 Quick start This quickly covers the standard steps for installing and deploying Kea For further details full customizations and troubleshoot ing see the respective chapters in the Kea guide 2 1 Quick start guide for DHCPv4 and DHCPV6 services Install required run time and build dependencies See Section 3 3 for details Download Kea source tarball from ISC org downloads page or ISC ftp server Extract the tarball For example tar xvzf kea 0 9 2 tar gz Go into t
69. Dhcp4 lease database parameters The type of the database must be set to mysql or postgresql e g Dhcp4 lease database type mysql Next the name of the database to hold the leases must be set this is the name used when the lease database was created see Section 4 3 2 1 or Section 4 3 3 1 Dhcp4 lease database name database name If the database is located on a different system to the DHCPv4 server the database host name must also be specified although it should be noted that this configuration may have a severe impact on server performance Dhcp4 lease database host remote host name The usual state of affairs will be to have the database on the same machine as the DHCPv4 server In this case set the value to the empty string pinot s I Mlease cemalsasers E Masia a Mo soa lo so J Finally the credentials of the account under which the server will access the database should be set Dhcp4 lease database user user name password password If there is no password to the account set the password to the empty string This is also the default 7 2 3 Interface configuration The DHCPv4 server has to be configured to listen on specific network interfaces The simplest network interface configuration tells the server to listen on all available interfaces Kea Administrator Reference Manual 26 113 ICA inte
70. HCPREQUEST This recovery mechanism allows the server to fully recover from a case where reservations conflict with the existing leases This procedure takes time and will roughly take as long as renew timer value specified The best way to avoid such recovery is to not define new reservations that conflict with existing leases Another recommendation is to use out of pool reservations If the reserved address does not belong to a pool there is no way that other clients could get this address note that having multiple reservations for the same address is not allowed 7 3 3 Reserving a hostname When the reservation for the client includes the hostname the server will assign this hostname to the client and send it back in the Client FQDN or Hostname option depending on which of them the client has sent to the server The reserved hostname always takes precedence over the hostname supplied by the client or the autogenerated from the IPv4 address hostname The server qualifies the reserved hostname with the value of the qualifying suffix parameter For example the following subnet configuration MSubneea sa f Suances VIO O60 0 244 Neoolste E odos 10 00 10 10 00 100 1 reservations hw address aa bb cc dd ee ff hostname alice laptop Jl Woalhicpo dems y Al enable updates true gqualifying suffix example isc org will result in assigning the alice laptop example isc org hostname to
71. Kea Administrator Reference Manual Kea Administrator Reference Manual Kea Administrator Reference Manual Copyright O 2010 2015 Internet Systems Consortium Inc Kea Administrator Reference Manual iii Contents 1 Introduction 1 11 Supported Platlorms e e 4 25 94 86 ea Syd tte Bae ede eee Yas BE Oe BEGGS k 1 1 2 Required Software at Run time oaaae 1 1 3 Kea SoftWare papsi seai eaaa Be ad a y a a E E a Ga OS a tg a oe 2 2 Quick start 3 2 1 Quick start guide for DHCPv4 and DHCPv6 services e 3 2 2 Running Kea servers directly ee 4 3 Installation 5 Soko Packages maior dns o e da rd ee SH 4 ek eee oD 5 3 2 Install Hieratehy e eeg eee eee ERROR REE AES ORE ED RE ESS EE A See eS Y 3 3 3 Building Requirements asas A we SR i a a OAR doe Boar AG wha Gok amp ak 3 3 4 Installation from Source osaa 6 341 Download Tar File e ceseco k oe cec eR RR ee RS eR oaa al i a 6 34 2 Reeve from Gite aa A e E A ees da a E 6 3 4 3 Configure before the build ee 7 3 44 Build 4 zk ee a wok bok Bw a UR d a Sh obi ia ea a a Re ew Sek bot i e de 7 SAS Install ca 2 ara ra Re e a ae e a a 8 3 5 Selecting the Configuration Backend 2 2 ee 8 3 6 DHCP Database Installation and Configuration 2 0 2 0 2 00 0 00000 000000000 8 3 6 1 Building with MySQL Support 2 2 2 2 2 2 2 0 0 0 0000000000000 0000004 8 3 6 2 Building with PostgreSQL Support 9 4 Ke
72. NS requests e port The port on which the server listens for DDNS requests It defaults to the standard DNS service port of 53 To create a new reverse DNS Server one must first add a new server element to the domain and fill in its parameters If for example the service is running at 172 88 99 10 then set it as follows DEcpD ARS a i reverse_ddns ddns_domains Vinee MO DAS DO Os ca y Sy aca Mu dns_servers 1 hostname ip address 172 88 99 10 port 53 Note As stated earlier hostname is not yet supported so the parameter ip_ address must be set to the address of the DNS server Kea Administrator Reference Manual 9 2 5 Example DHCP DDNS Server Configuration This section provides an example DHCP DDNS server configuration based on a small example network Let s suppose our example network has three domains each with their own subnet Domain Subnet Forward DNS Servers Reverse DNS Servers four example com 192 0 2 0 24 172 16 1 5 172 16 2 5 172 16 1 5 172 16 2 5 six example com 2001 db8 1 64 3001 1 50 3001 1 51 example com 192 0 0 0 16 172 16 2 5 172 16 2 5 We need to construct three forward DDNS Domains As discussed earlier FQDN to domain matching is based on the longest Table 9 1 Our example network DDNS Domain Name DNS Servers four example com 172 16 1 5 172 16 2 5 six example com 3001 1 50 o ae
73. The resolvable host name of the DNS server This value is not yet implemented e ip_address The IP address at which the server listens for DDNS requests This may be either an IPv4 or an IPv6 address e port The port on which the server listens for DDNS requests It defaults to the standard DNS service port of 53 To create a new forward DNS Server one must add a new server element to the domain and fill in its parameters If for example the service is running at 172 88 99 10 then set it as follows LD hie pD ARS forward dans 4 ddns_domains Kea Administrator Reference Manual 91 113 name other example com key name jes dns_servers hostname ip_address 172 88 99 10 port 53 Note As stated earlier hostname is not yet supported so the parameter ip_ address must be set to the address of the DNS server 9 2 4 Reverse DDNS The Reverse DDNS section is used to configure D2 s reverse update behavior and the concepts are the same as for the forward DDNS section Currently it contains a single parameter the catalog of reverse DDNS Domains which is a list of structures DhcpDdns reverse_ddns ddns_domains By default this list is empty which will cause the server to ignore the reverse update portions of requests 9 2 4 1 Adding Reverse DDNS Domains A reverse DDNS Domain maps a reverse DNS zone to a set of DNS servers which maintain the revers
74. a Database Administration 10 4 1 Databases and Database Version Numbers 2 2 a 10 42 Thekeaadmin TOOL oi Es dom e ena p a A a eee ee BE e e a a 10 4 3 Supported Databases s sss apai ia ep ae e 44 G e a De BS Aba E eS 11 431 me mile s re reada a 8644 6662 04 be a a aa 11 A432 MySQL citan aaa RE a a ao AA Shoe BAR e Ac da 11 4 3 2 1 First Time Creation of Kea Database 0 00 a al Kea Administrator Reference Manual iv 4 3 2 2 Upgrading a MySQL Database from an Earlier Version of Kea o 12 4 3 3 PostereSQlo lt htm o A A EKER EH eS SS 12 4 3 3 1 Manually Create the PostgreSQL Database and the Kea User 12 4 3 3 2 Initialize the PostgreSQL Database Using kea admin o 14 4 3 3 3 Upgrading a PostgreSQL Database from an Earlier Version of Kea 14 4 3 4 Limitations related to the use of the SQL databases es 14 5 Kea configuration 15 5 1 JSON configuration backend noaa 2 15 3 1 0 JSON syntax gk ee bbe ee bee BS e REED Ae Re ee eae ee a eh ae a 15 5 1 2 Simplified Notation esv es d bee ee ee ee wa ea ee 16 6 Managing Kea with keactrl 17 6l OVEIVIEW 26244 2G a mei bee bee hata he ee wots ee eee Aa eee ok 17 6 2 Command Line Options 17 6 3 The keactrl Configuration File lt s s s e ss cearo 0 0 0 0 00000000022 ee 17 64 Commands 2 2 66246 ci a o be E a e eae oa e dee a 18 6 5 Overriding the Server Selection
75. ach subnet definition in the list has several attributes associated with it so it is a structure and is opened and closed with braces At minimum a subnet definition has to have at least two parameters subnet that defines the whole subnet and pool which is a list of dynamically allocated pools that are governed by the DHCP server The example contains a single subnet Had more than one been defined additional elements in the subnet6 parameter would be specified and separated by commas For example to define two subnets the following syntax would be used subretors If OSOS ten ale 200 close y 112W l Telomere 3 Ann sellos ds e a o Hoolas E Wools Y2OO il gcloisss 28 3 1 200 Lc 3 28 gacsiciese de ll vsubner WAN 2s 2 Saw interface eth0 Kea Administrator Reference Manual 57 113 Note that indentation is optional and is used for aesthetic purposes only In some cases in may be preferable to use more compact notation After all parameters are specified we have two contexts open global and Dhcp6 hence we need two closing curly brackets to close them In a real life configuration file there most likely would be additional components defined such as Logging or DhcpDdns so the closing brace would be followed by a comma and another object definition 8 2 2 Lease Storage All leases issued by the server are stored in the lease database Currently there are three database backends available memfile
76. aken to specify proper unicast addresses The server will attempt to bind to those addresses specified without any additional checks This approach is selected on purpose so the software can be used to communicate over uncommon addresses if the administrator so desires 8 2 6 Subnet and Address Pool The essential role of a DHCPV6 server is address assignment For this the server has to be configured with at least one subnet and one pool of dynamic addresses to be managed For example assume that the server is connected to a network segment that uses the 2001 db8 1 64 prefix The Administrator of that network has decided that addresses from range 2001 db8 1 1 to 2001 db8 1 ffff are going to be managed by the Dhcp6 server Such a configuration can be achieved in the following way Macs f subnet6 subnet 2001 db8 1 64 pools pool 2001 db8 1 1 2001 db8 1 ffff f Note that subnet is defined as a simple string but the pool parameter is actually a list of pools for this reason the pool definition is enclosed in square brackets even though only one range of addresses is specified Each pool is a structure that contains the parameters that describe a single pool Currently there is only one parameter pool which gives the range of addresses in the pool Additional parameters will be added in future releases of Kea It is possible to define more than one pool in a subnet continuing the previous example
77. alifying suffix example The default values for the dhcp ddns section are as follows server ip 127 0 0 1 server port 53001 menn sender ip sender port 0 max queue size 1024 ner protocol UDP ner format JSON Kea Administrator Reference Manual 73 113 override no update false override client update false replace client name false men generated prefix myhost 8 2 19 1 DHCP DDNS Server Connectivity In order for NCRs to reach the D2 server kea dhcp6 must be able to communicate with it kea dhcp6 uses the following configuration parameters to control how it communications with D2 enable updates determines whether or not kea dhcp6 will generate NCRs If missing this value is assumed to be false hence DDNS updates are disabled To enable DDNS updates set this value to true server ip IP address on which D2 listens for requests The default is the local loopback interface at address 127 0 0 1 You may specify either an IPv4 or IPv6 address server port port on which D2 listens for requests The default value is 53001 sender ip IP address which kea dhcp6 should use to send requests to D2 The default value is blank which instructs kea dhcp6 to select a suitable address sender port port which kea dhcp6 should use to send requests to D2 The default value of 0 instructs kea dhcp6 to select a suitable port max queue size maximum number of reque
78. ame or option code to identify an option This parameter may be left unspecified if the name parameter is specified However this also requires that the particular option has its definition it is either a standard option or an administrator created a definition for the option using an option def structure as the option definition associates an option with a particular name It is possible to configure an option for which there is no definition unspecified option format Configuration of such options requires the use of option code Kea Administrator Reference Manual 69 113 e space if the option space is unspecified it will default to dhcp6 which is an option space holding DHCPv6 standard options e data if the option data is unspecified it defaults to an empty value The empty value is mostly used for the options which have no payload boolean options but it is legal to specify empty values for some options which carry variable length data and which spec allows for the length of 0 For such options the data parameter may be omitted in the configuration e csv format if this value is not specified and the definition for the particular option exists the server will assume that the option data is specified as a list of comma separated values to be assigned to individual fields of the DHCP option If the definition does not exist for this option the server will assume that the data parameter contains the option payload in the b
79. an error is encountered e g requested statistic was not found the server will return a status code of 1 error and the text field will contain the error description 12 3 4 statistic get all command statistic get all command retrieves all statistics recorded An example command may look like this ecmencs Searasicaio qsrt cull arguments The server will respond with details of all recorded statistics with result set to 0 indicating that it iterated over all statistics even when the total number of statistics is zero 12 3 5 statistic reset all command statistic reset command sets all statistics to their neutral values O for integer 0 0 for float OhOmOsOus for time duration and for string type An example command may look like this command statistic reset all arguments If the operation is successful the server will respond with a status of 0 indicating success and an empty parameters field If an error is encountered the server will return a status code of 1 error and the text field will contain the error description 12 3 6 statistic remove all command statistic remove all command attempts to delete all statistics An example command may look like this command statistic remove all arguments If the removal of all statistics was successful the server will respond with a status of 0 indicating success and an empty pa rameters field If an error is encountered the s
80. an optional reservations array in the Subnet6 structure Each element in that array is a structure that holds information about a single host In particular such a structure has to have an indentifer that uniquely identifies a host In DHCPv6 context such an identifier is a hardware MAC address or a DUID Also either one or more addresses or prefixes should be specified It is possible to specify a hostname Additional capabilities are planned The following example shows how to reserve addresses and prefixes for specific hosts subnet6 mom ANO Lc less pus Vooolss pogl s V200 scioss lgs L00 1 Melos es Moret 2001 ciosg LSM 2 prefix len 56 delegated len 64 i ly reservations duid 01 02 03 04 05 0A 0B 0C 0D 0E ip addresses 2001 db8 1 100 Do hw address 00 01 02 03 04 05 ip addresses 2001 db8 1 101 duid 01 02 03 04 05 06 07 08 09 0A ip addresses 2001 db8 1 102 Kea Administrator Reference Manual 77 113 prefixes 2001 db8 2 abcd 64 hostname foo example com This example makes 3 reservations The first one reserves 2001 db8 1 100 address for the client using DUID 01 02 03 04 05 0A 0B 0C The second one also reserves an address but does so using MAC or hardware address rather than DUID The third example is most advanced It reserves an address a prefix and a hostname at the same time Note that DHCPv6 allows for
81. asons why this identification is required and the most important ones are listed below e When the client contacts the server to allocate a new lease the server must store the client identification information in the lease database as a search key e When the client is trying to renew or release the existing lease the server must be able to find the existing lease entry in the database for this client using the client identification information as a search key e Some configurations use static reservations for the IP addreses and other configuration information The server s administrator uses client identification information to create these static assignments e In the dual stack networks there is often a need to correlate the lease information stored in DHCPv4 and DHCPV6 server for a particular host Using common identification information by the DHCPv4 and DHCPv6 client allows the network administrator to achieve this correlation and better administer the network DHCPv4 makes use of two distinct identifiers which are placed by the client in the queries sent to the server and copied by the server to its responses to the client chaddr and client identifier The former was introduced as a part of the BOOTP specification and it is also used by DHCP to carry the hardware address of the interface used to send the query to the server MAC address for the Ethernet The latter is carried in the Client identifier option introduced in the RF
82. ave quite varied expectations regarding the client and is even likely to be written in languages different than C or C Therefore we only provide examples how one can take advantage of the API The easiest way is to use a tool called socat a tool available from socat homepage but it is also widely available in Linux and BSD distributions Once Kea is started one could connect to the control interface using the following command socat UNIX path to the kea socket where path to the kea socket is the path specified in the Dhcp4 control socket socket name parameter in the Kea configura tion file It is also easy to open UNIX socket programmatically An example of such a simplistic client written in C is available in the Kea Developer s Guide chapter Control Channel Overview section Using Control Channel 13 3 Commands supported by both DHCPv4 and DHCPv6 servers 13 3 1 list commands command list commands command retrieves a list of all commands supported by the server It does not take any arguments An example command may look like this command list commands arguments The server will respond with a list of all supported commands The arguments element will be a list of strings Each string will convey one supported command 13 3 2 shutdown command shutdown command instructs the server to initiate its shutdown procedure It is the equivalent of sending a SIGTERM singal to the process This command does no
83. ce after the last comment Everything defined between those lines is considered to be the Dhcp4 configuration In the general case the order in which those parameters appear does not matter There are two caveats here though The first one is to remember that the configuration file must be well formed JSON That means that the parameters for any given scope must be separated by a comma and there must not be a comma after the last parameter When reordering a configuration file keep in mind that moving a parameter to or from the last position in a given scope may also require moving the comma The second caveat is that 1t is uncommon although legal JSON to repeat the same parameter multiple times If that happens the last occurrence of a given parameter in a given scope is used while all previous instances are ignored This is unlikely to cause any confusion as there are no real life reasons to keep multiple copies of the same parameter in your configuration file Moving onto the DHCPv4 configuration elements the very first few elements define some global parameters valid lifetime defines for how long the addresses leases given out by the server are valid If nothing changes a client that got an address is allowed to use it for 4000 seconds Note that integer numbers are specified as is without any quotes around them renew timer and rebind timer are values that define T1 and T2 timers that govern when the client will begin the renewal and
84. change the corresponding values in the DHCP servers dhcp ddns configuration section 9 2 2 TSIG Key List A DDNS protocol exchange can be conducted with or without TSIG defined in RFC 2845 This configuration section allows the administrator to define the set of TSIG keys that may be used in such exchanges To use TSIG when updating entries in a DNS Domain a key must be defined in the TSIG Key List and referenced by name in that domain s configuration entry When D2 matches a change request to a domain it checks whether the domain has a TSIG key associated with it If so D2 will use that key to sign DNS update messages sent to and verify responses received from the domain s DNS server s For each TSIG key required by the DNS servers that D2 will be working with there must be a corresponding TSIG key in the TSIG Key list As one might gather from the name the tsig_key section of the D2 configuration lists the TSIG keys Each entry describes a TSIG key used by one or more DNS servers to authenticate requests and sign responses Every entry in the list has three parameters e name a unique text label used to identify this key within the list This value is used to specify which key if any should be used when updating a specific domain So long as it is unique its content is arbitrary although for clarity and ease of maintenance it is recommended that it match the name used on the DNS server s It cannot be blank e algorithm
85. configuration structure as the server uses that information to process clients requests It defines all subnets from which the server is expected to receive DHCP requests The subnets are specified with the subnet4 parameter It is a list so it starts and ends with square brackets Each subnet definition in the list has several attributes associated with it so it is a structure and is opened and closed with braces At a minimum a subnet definition has to have at least two parameters subnet that defines the whole subnet and pools which is a list of dynamically allocated pools that are governed by the DHCP server The example contains a single subnet Had more than one been defined additional elements in the subnet4 parameter would be specified and separated by commas For example to define three subnets the following syntax would be used subnet4 DOSIS f poo l s VETA Os 2oi 192 0 2 200 E I suse a Wile 0 2 0 24 Moors tocan 41920 3 LOO 192 0 3 200 F 1 Uemomec4 es 192 0 3 10 2400 poolis uean Tone MB 0 gt LIA O Aa Uwina g Wille OA O 2aw After all parameters are specified we have two contexts open global and Dhcp4 hence we need two closing curly brackets to close them In a real life configuration file there most likely would be additional components defined such as Logging or DhcpDdns so the closing brace would be followed by a comma and another object definition Kea Administrator Reference Manual
86. d or manually To create the tables manually enter the following command Note that PostgreSQL will prompt you to enter the new user s password you specified in Step 3 When the command completes you will be returned to the shell prompt You should see output similar to following psql d database name U user name f path to kea share kea scripts pgsql gt dhcpdb_create pgsql Password for user user name CREATE ABLE CREATE INDEX CREATE INDEX CREATE TABLE CREATE INDEX CREATE TABLE START TRANSACTION INSERT 0 1 TNSER TEOR INSERT 0 1 COMMIT CREATE TABLE START TRANSACTION INSERT 0 1 COMMIT path to kea is the location where you installed Kea If instead you encounter an error like psql FATAL no pg_hba conf entry for host local user user name database database name SSL off you will need to alter the PostgreSQL configuration Kea uses password authentication when connecting to the database and must have the appropriate entries added to PostgreSQL s pg_hba conf file This file is normally located in the primary data directory for your PostgreSQL server The precise path may vary but the default location for PostgreSQL 9 3 on Centos 6 5 is var lib pgsql1 9 3 data pg_hba conf Assuming Kea is running on the same host as PostgreSQL adding lines similar to following should be sufficient to provide password a
87. d the contained value used whenever the server is subsequently started Kea Administrator Reference Manual 80 113 It is unlikely that this parameter should ever need to be changed However if such a need arises stop the server edit the file and restart the server The file is named kea dhcp6 serverid and by default is stored in the var subdirectory of the directory in which Kea is installed This can be changed when Kea is built by using localstatedir on the configure command line The file is a text file that contains double digit hexadecimal values separated by colons This format is similar to typical MAC address format Spaces are ignored No extra characters are allowed in this file 8 5 Stateless DHCPv6 Information Request Message Typically DHCPv6 is used to assign both addresses and options These assignments leases have state that changes over time hence their name stateful DHCPv6 also supports a stateless mode where clients request configuration options only This mode is considered lightweight from the server perspective as it does not require any state tracking hence its name The Kea server supports stateless mode Clients can send Information Request messages and the server will send back answers with the requested options providing the options are available in the server configuration The server will attempt to use per subnet options first If that fails for whatever reason it will then try to provide o
88. default DHCPv6 ports will not be able to handle regular DHCPv6 queries y prints out Kea version and exits V prints out Kea extended version with additional parameters and exits W prints out Kea configuration report and exits The V command returns the versions of the external libraries dynamically linked The W command describes the environment used to build Kea This command displays a copy of the config report file produced by configure that is embedded in the executable binary The config report may also be accessed more directly The following command may be used to extract this information The binary path may be found in the install directory or in the 1ibs subdirectory in the source treee For example kea src bin dhcp6 libs kea dhcp6 strings path kea dhcp6 sed n s p When running in a console the server can be shut down by pressing ctrl c It detects the key combination and shuts down gracefully On start up the server will detect available network interfaces and will attempt to open UDP sockets on all interfaces mentioned in the configuration file Since the DHCPv6 server opens privileged ports it requires root access Make sure you run this daemon as root During startup the server will attempt to create a PID file of the form localstatedir conf name kea dhcp6 pid where e localstatedir The value as passed into the build configure script It defaults defaults to usr local var Note tha
89. duced in Kea 0 9 2 beta It allows issuing specific management commands like statistics re trieval reconfiguration or shutdown For more details see Chapter 13 Currently the only supported communication channel type is UNIX stream socket By default there are no sockets open To instruct Kea to open a socket the following entry in the configuration file can be used Dhcep4 Control socket socket type unix socket name path to the unix socket lo subnet4 l The length of the path specified by the socket name parameter is restricted by the maximum length for the unix socket name on your operating system i e the size of the sun_path field in the sockaddr_un structure decreased by 1 This value varies on different operating systems between 91 and 107 characters The typical values are 107 on Linux and 103 on FreeBSD Communication over control channel is conducted using JSON structures See the Control Channel section in the Kea Developer s Guide for more details DHCPv4 server supports statistic get statistic reset statistic remove statistic get all statistic reset all and statistic remove all specified in Section 12 3 It also supports list commands and shutdown specified in Section 13 3 1 and Section 13 3 2 respectively 7 8 Supported DHCP Standards The following standards are currently supported Dynamic Host Configuration Protocol RFC 2131 Supported messages are DHCPDISCOVER 1 DHCPOFFER
90. e Ifc interval is too short The server would recover from this by skipping the new cleanup when it detects that the previous cleanup is still in progress But this implies that the actual cleanups will be triggered more rarely than configured Moreover triggering a new cleanup adds an overhead to the server which will not be able to respond to new requests for a short period of time when the new cleanup process is spawned Therefore it is recommended that the Ifc interval value is selected in a way that would allow for completing the cleanup before the new cleanup is triggered The LFC is performed by a separate process in background to avoid performance impact on the server process In order to avoid the conflicts between the two processes both using the same lease files the LFC process operates on the copy of the original lease file rather than on the lease file used by the server to record lease updates There are also other files being created as a side effect of the lease file cleanup The detailed description of the LFC is located on the Kea wiki http kea isc org wiki LFCDesign 7 2 2 2 Database Configuration Note Database access information must be configured for the DHCPv4 server even if it has already been configured for the DHCPv6 server The servers store their information independently so each server can use a separate database or both servers can use the same database Database configuration is controlled through the
91. e though as there s small chance that the DHCPNAK may be lost if the network is lossy If that happens the client will not receive any responses so it will retransmit its DHCPREQUEST packet Once the DHCPNAK is received by the Host A it will then revert to the server discovery and will eventually get a different address Besides allocating a new lease the server will also remove the old one As a result the address 192 0 2 10 will be no longer used When Host B tries to renew its temporarily assigned address the server will detect that it has a valid lease but there is a reservation for a different address The server will send DHCPNAK to inform Host B that its address is no longer usable but will keep its lease again the DHCPNAK may be lost so the server will keep it until the client returns for a new address The Host B will revert to the server discovery phase and will eventually send a DHCPREQUEST message This time the server will find out that there is a reservation for that host and the reserved address 192 0 2 10 is not used so it will be granted It will also remove the lease for the temporarily assigned address that the Host B previously obtained This recovery will succeed even if other hosts will attempt to get the reserved address Had the Host C requested address 192 0 2 10 after the reservation was made the server will either offer a different address when responding to DHCPDISCOVER or would send DHCPNAK when responding to D
92. e DNS data address to name mapping for that zone You will need one reverse DDNS Domain for each zone you wish to service It may very well be that some or all of your zones are maintained by the same servers even then you will still need one DDNS Domain entry for each zone Remember that matching a request to the appropriate server s is done by zone and a DDNS Domain only defines a single zone This section describes how to add Reverse DDNS Domains Repeat these steps for each Reverse DDNS Domain desired Each Reverse DDNS Domain has the following parameters name The fully qualified reverse zone that this DDNS Domain can update This is the value used during reverse matching which will compare it with a reversed version of the request s lease address The zone name should follow the appropriate standards for example to to support the IPv4 subnet 172 16 1 the name should be 1 16 172 in addr arpa Similarly to support an IPv6 subent of 2001 db8 1 the name should be 1 0 0 0 8 B D 0 1 0 0 2 ip6 arpa Whatever the name it must be unique within the catalog key_name If TSIG should be used with this domain s servers then this value should be the name of that key from the TSIG Key List If the value is blank the default TSIG will not be used in DDNS conversations with this domain s servers Currently this value is not used as TSIG has not been implemented dns_servers a list of one or more DNS servers which can conduct the ser
93. e an indentifer that uniquely identifies a host In DHCPv4 context such an identifier is a hardware or MAC address In most cases also an address will be specified It is possible to specify a hostname Additional capabilities are planned Kea Administrator Reference Manual 46 113 The following example shows how to reserve addresses for specific hosts Ssporeta Y Molist A Mewes Willen 2 12 0 2200 Je Vy STD g LOZ Oo 2 0 24 interface eth0 reservations hw address la lb 1c 1d le 1f ip address 192 0 2 202 hw address 0a 0b 0c 0d 0e 0f ip address 192 0 2 100 hostname alice laptop The first entry reserves the 192 0 2 202 address for the client that uses MAC adress of la 1b 1c 1d 1e 1f The second entry reserves the address 192 0 2 100 and the hostname of alice laptop for client using MAC address 0a 0b 0c 0d 0e 0f Note that if you plan to do DNS updates it is strongly recommended for the hostnames to be unique Making a reservation for a mobile host that may visit multiple subnets requires a separate host definition in each subnet it is expected to visit It is not allowed to define multiple host definitions with the same hardware address in a single subnet It is a valid configuration if such definitions are specified in different subnets though Adding host reservation incurs a performance penalty In principle when the server that does not support host reservation responds t
94. e following instructs keactrl to stop the kea dhcp4 and kea dhcp6 servers and leave the kea dhep ddns server running keactrl stop s dhcp4 dhcp6 Similarly the following will only start the kea dhcp4 and kea dhcp ddns servers and not kea dhcp6 keactrl start s dhcp4 dhcp_ddns Note that the behavior of the s switch with the start and reload commands is different to 1ts behavior with the stop command On start and reload keactrl will check if the servers given as parameters to the s switch are enabled in the keactrl configuration file if not the server will be ignored For stop however this check is not made the command is applied to all listed servers regardless of whether they have been enabled in the file The following keywords can be used with the s command line option e dhcp4 for kea dhcp4 e dhcp6 for kea dhcp6 e dhcp_ddns for kea dhcp ddns e all for all servers default Kea Administrator Reference Manual 21 113 Chapter 7 The DHCPv4 Server 7 1 Starting and Stopping the DHCPv4 Server It is recommended that the Kea DHCPv4 server be started and stopped using keactrl described in Chapter 6 However it is also possible to run the server directly it accepts the following command line switches c file specifies the configuration file This is the only mandatory switch d specifies whether the server logging should be switched to debug verbose mode In verbose mode the logging severity and deb
95. e libraries to see if this is the case The next section describes how to configure hooks libraries If you are interested in writing your own hooks library information can be found in the Kea Developer s Guide 11 2 Configuring Hooks Libraries The hooks libraries for a given process are configured using the hooks libraries keyword in the configuration for that process Note that the word hooks is plural The value of the keyword is an array of strings each string corresponding to a hooks library For example to set up two hooks libraries for the DHCPV4 server the configuration would be Dhcp4 hooks libraries opt charging so opt local notification so Note At present the libraries are specified as a simple list A future version of Kea will support the capability of specifying a set of parameters for each library When that is added it is likely that the syntax for specifying hooks libraries will change Notes Kea Administrator Reference Manual 97 113 e The full path to each library should be given e As noted above order may be important consult the documentation for each library e An empty list has the same effect as omitting the hooks libraries configuration element all together At the present time only the kea dhcp4 and kea dhcp6 processes support hooks libraries Kea Administrator Reference Manual 98 113 Chapter 12 Statistics 12 1 Statistics Overview Both Kea DHCP
96. e primary use case for such a scenario is cable networks There are two classes of devices the cable modem itself which should be handed a lease from subnet A and all other devices behind the modem that should get a lease from subnet B That segregation is essential to prevent overly curious users from playing with their cable modems For details on how to set up class restrictions on subnets see Section 7 2 13 1 7 2 13 1 Limiting Access to IPv4 Subnet to Certain Classes In certain cases it beneficial to restrict access to certain subnets only to clients that belong to a given subnet For details on client classes see Section 7 2 13 This is an extension of a previous example from Section 7 2 6 Let s assume that the server is connected to a network segment that uses the 192 0 2 0 24 prefix The Administrator of that network has decided that addresses from range 192 0 2 10 to 192 0 2 20 are going to be managed by the Dhcp4 server Only clients belonging to client class VENDOR_CLASS_docsis3 0 are allowed to use this subnet Such a configuration can be achieved in the following way Dhcp4 subnet4 subnet 192 0 2 0 24 pools pool 192 0 2 10 192 0 2 20 client class VENDOR_CLASS _docsis3 0 Care should be taken with client classification as it is easy for clients that do not meet class criteria to be denied any service altogether 7 2 14 Configuring DHCPv4 for DDNS As mentioned earlier kea dhcp4 can be co
97. e reload command sends the SIGHUP signal to the servers that are enabled in the keactrl configuration file and are currently running When a server receives the SIGHUP signal it re reads its configuration file and if the new configuration is valid uses the new configuration A reload is executed as follows keactrl reload INFO keactrl Reloading kea dhcp4 INFO keactrl Reloading kea dhcp6 INFO keactrl Reloading kea dhcp ddns If any of the servers are not running an informational message is displayed as in the reload command output below keactrl stop INFO keactrl kea dhcp4 isn t running INFO keactrl kea dhcp6 isn t running INFO keactrl kea dhcp ddns isn t running Note Currently keactrl does not report configuration failures when the server is started or reconfigured To check if the servers configuration succeeded the Kea log must be examined for errors By default this is written to the syslog file Sometimes it is useful to check which servers are running The status reports this typical output looking like keactrl status DHCPv4 server active DHCPv6 server inactive DHCP DDNS active Kea configuration file usr local etc kea kea conf keactrl configuration file usr local etc kea keactrl conf Kea Administrator Reference Manual 20 113 6 5 Overriding the Server Selection The optional s switch allows the selection of the servers to which keactrl command is issued For example th
98. e same through several Kea revisions Likewise it is possible that the version of backend database may go up several revisions during a Kea upgrade Versions for each database are independent so an increment in the MySQL database version does not imply an increment in that of PostgreSQL Backend versions are specified in a major minor format The minor number is increased when there are backward compatibile changes introduced For example the addition of a new index It is desirable but not mandatory to to apply such a change you can run on older database version if you want to Although in the example given running without the new index may be at the expense of a performance penalty On the other hand the major number is increased when an incompatible change 1s introduced for example an extra column is added to a table If you try to run Kea software on a database that is too old as signified by mismatched backend major version number Kea will refuse to run administrative action will be required to upgrade the database 4 2 The kea admin Tool To manage the databases Kea provides the kea admin tool It is able to initialize a new database check its version number perform a database upgrade and dump lease data to a text file kea admin takes two mandatory parameters command and backend Additional non mandatory options may be specified Currently supported commands are lease init Initializes a new lease database Useful during
99. e when sending requests to D2 Currently only UDP is supported TCP may be available in an upcoming release ncr protocol packet format to use when sending requests to D2 Currently only JSON format is supported Other formats may be available in future releases Kea Administrator Reference Manual 41 113 By default kea dhcp ddns is assumed to be running on the same machine as kea dhcp4 and all of the default values mentioned above should be sufficient If however D2 has been configured to listen on a different address or port these values must be altered accordingly For example if D2 has been configured to listen on 192 168 1 10 port 900 the following configuration would be required Dhcp4 lane adas E server ip 192 168 1 10 server port 900 7 2 14 2 When Does the kea dhcp4 Server Generate DDNS Requests kea dhcp4 follows the behavior prescribed for DHCP servers in RFC 4702 It is important to keep in mind that kea dhcp4 provides the initial decision making of when and what to update and forwards that information to D2 in the form of NCRs Carrying out the actual DNS updates and dealing with such things as conflict resolution are within the purview of D2 itself Chapter 9 This section describes when kea dhcp4 will generate NCRs and the configuration parameters that can be used to influence this decision It assumes that the enable updates parameter is true In general kea dhcp4 will generate DDNS update reques
100. each the D2 server kea dhcp4 must be able to communicate with it kea dhcp4 uses the following configuration parameters to control how it communications with D2 enable updates determines whether or not kea dhcp4 will generate NCRs By default this value is false hence DDNS updates are disabled To enable DDNS updates set this value to true server ip IP address on which D2 listens for requests The default is the local loopback interface at address 127 0 0 1 You may specify either an IPv4 or IPv6 address server port port on which D2 listens for requests The default value is 53001 sender ip IP address which kea dhcp4 should use to send requests to D2 The default value is blank which instructs kea dhcp4 to select a suitable address sender port port which kea dhcp4 should use to send requests to D2 The default value of 0 instructs kea dhcp4 to select a suitable port max queue size maximum number of requests allowed to queue waiting to be sent to D2 This value guards against requests accumulating uncontrollably if they are being generated faster than they can be delivered If the number of requests queued for transmission reaches this value DDNS updating will be turned off until the queue backlog has been sufficiently reduced The intention is to allow the kea dhcp4 server to continue lease operations without running the risk that its memory usage grows without limit The default value is 1024 ncr format socket protocol us
101. eamon for logging inbound client packets that were dropped or to which the server responded with a DHCPNAK The allows adminstrators to configure a separate log output that contains only packet drop and reject entries kea dhcp4 callouts this logger is used to log messages pertaining to the callouts registration and execution for the particular hook point kea dhcp4 ddns this logger is used by the DHCPv4 server to log messages related to the Client FQDN and Hostname option processing It also includes log messages related to the relevant DNS updates kea dhcp4 dhep4 this is the logger by the DHCPv4 server deamon to log basic operations kea dhcp4 dhepsrv this is a base logger for the libdhcpsrv library kea dhcp4 hooks this logger is used to log messages related to management of hooks libraries e g registration and deregis tration of the libraries and to the initialization of the callouts execution for various hook points within the DHCPv4 server kea dhcp4 hosts this logger is used within the libdhcpsrv and it logs messages related to the management of the DHCPv4 host reservations i e retrieval of the resevations and adding new reservations kea dhcp4 leases this logger is used by the DHCPv4 server to log messages related to the lease allocation The messages include detailed information about the allocated or offered leases errors during the lease allocation etc kea dhcp4 options this logger is used by the DHCPv4 server
102. ed lifetime 3000 valid lifetime 4000 renew timer 1000 rebind timer 2000 tsubrete o A Mole s 1 ocol AO AO F il uo 200 css pour Jl Ihe DHCPv6 specific configuration ends here Logger parameters that could be shared among several components start here This section is used by both the DHCPv4 and DHCPv6 servers Locas A loggers Wroveuare ly WE severity DEBUG Hl Logger parameters end her The whole configuration structure ends here More examples are available in the installed share doc kea examples directory To avoid repetition of mostly similar structures examples in the rest of this guide will showcase only the subset of parameters ap propriate for a given context For example when discussing the IPv6 subnets configuration in DHCP v6 only subnet6 parameters will be mentioned It is implied that the remaining elements the global map that holds Dhcp6 Logging and possibly DhcpDdns are present but they are omitted for clarity Usually locations where extra parameters may appear are denoted with an ellipsis 5 1 2 Simplified Notation It is sometimes convenient to refer to a specific element in the configuration hierarchy Each hierarchy level is separated by a slash If there is an array a specific instance within that array is referenced by a number in square brackets with numbering starting at zero For example in the above configuration the valid lifetime
103. ed on a different system than the DHCPV6 server the database host name must also be specified although 1t should be noted that this configuration may have a severe impact on server performance Dhcp6 lease database host remote host name The usual state of affairs will be to have the database on the same machine as the DHCPV6 server In this case set the value to the empty string DATE e SS dai ans IA A O SE eno In cos Finally the credentials of the account under which the server will access the database should be set Dhcp6 lease database user user name password password If there is no password to the account set the password to the empty string This is also the default 8 2 3 Interface selection The DHCPv6 server has to be configured to listen on specific network interfaces The simplest network interface configuration instructs the server to listen on all available interfaces Kea Administrator Reference Manual 59 113 Maca af interfaces config arenas 1 Wee The asterisk plays the role of a wildcard and means listen on all interfaces However it is usually a good idea to explicitly specify interface names DING s xf interfaces config acerracess Edie ech Slums It is possible to use wildcard interface name asterisk concurrently with the actual interface names Unas Al interfaces config interfaces eth1 eth3 x
104. endencies configure when it succeeds displays a report with the building parameters This report is saved into config report and embedded into executable binaries e g kea dhcp4 3 4 4 Build After the configure step is complete build the executables from the C code and prepare the Python scripts by running the command make Kea Administrator Reference Manual 8 113 3 4 5 Install To install the Kea executables support files and documentation issue the command S make install Do not use any form of parallel or job server options such as GNU make s j option when performing this step doing so may cause errors Note The install step may require superuser privileges If required run ldconfig as root with usr local 1ib or with prefix lib if configured with prefix in etc 1d so conf or the relevant linker cache configuration file for your OS ldconfig Note If you do not run Idconfig where it is required you may see errors like the following program error while loading shared libraries libkea something so 1 cannot open shared object file No such file or directory 3 5 Selecting the Configuration Backend Kea 0 9 has introduced configuration backends that are switchable during the compilation phase Only one backend JSON is currently supported JSON JSON is the new default configuration backend that causes Kea to read JSON configuration files from disk It does no
105. er can use a given pool it will also be able to allocate the first typically network address address from that pool For example for pool 2001 db8 2 64 the 2001 db8 2 address may be assigned as well If you want to avoid this use the min max notation 8 2 7 Subnet and Prefix Delegation Pools Subnets may also be configured to delegate prefixes as defined in RFC 3633 A subnet may have one or more prefix delegation pools Each pool has a prefixed address which is specified as a prefix and a prefix length as well as a delegated prefix length delegated len must not be shorter that is it must be numerically greater or equal than prefix len If both delegated len and prefix len are equal the server will be able to delegate only one prefix The delegated prefix does not have to match the subnet prefix Below is a sample subnet configuration which enables prefix delegation for the subnet DA subneteo Usiolomsic s YA OO IL as pet oa pd pools prefix 3000 1 prefix len 64 delegated len 96 Kea Administrator Reference Manual 62 113 8 2 8 Standard DHCPv6 options One of the major features of a DHCPV6 server is to provide configuration options to clients Although there are several options that require special behavior most options are sent by the server only if the client explicitly requests them The following example shows how to configure DNS servers which is one of the most frequently used opt
106. er processes can determine the correct file to use even if one of the processes was interrupted before completing its task There are several additional arguments mostly for debugging purposes d Sets the logging level to debug v and V print out version stamps with V providing a longer form h prints out the usage string Kea Administrator Reference Manual 96 113 Chapter 11 Hooks Libraries 11 1 Introduction Although Kea offers a lot of flexibility there may be cases where its behavior needs customisation To accommodate this possibility Kea includes the idea of Hooks This feature lets Kea load one or more dynamically linked libraries known as hooks libraries and at various points in its processing hook points call functions in them Those functions perform whatever custom processing is required Hooks libraries are attached to individual Kea processes not to Kea as a whole This means for example that it is possible to associate one set of libraries with the DHCP4 server and a different set to the DHCP6 server Another point to note is that it is possible for a process to load multiple libraries When processing reaches a hook point Kea calls the hooks library functions attached to it If multiple libraries have attached a function to a given hook point Kea calls all of them in the order in which the libraries are specified in the configuration file The order may be important consult the documentation of th
107. er should listen to the DHCP messages The interfaces parameter specifies a list of network interfaces on which the server should listen Lists are opened and closed with square brackets with elements separated by commas Had we wanted to listen on two interfaces the interfaces config would look like this interfaces config tintertaces I gt VELROe equi The next couple of lines define the lease database the place where the server stores its lease information This particular example tells the server to use memfile which is the simplest and fastest database backend It uses an in memory database and stores leases on disk in a CSV file This is a very simple configuration Usually lease database configuration is more extensive and contains additional parameters Note that lease database is an object and opens up a new scope using an opening brace Its parameters just one in this example type follow Had there been more than one they would be separated by commas This scope is closed with a closing brace As more parameters follow a trailing comma is present Finally we need to define a list of IPv6 subnets This is the most important DHCP v6 configuration structure as the server uses that information to process clients requests It defines all subnets from which the server is expected to receive DHCP requests The subnets are specified with the subnet6 parameter It is a list so it starts and ends with square brackets E
108. erate a FODN using a configurable prefix and suffix To instruct kea dhcp6 to always generate a FQDN set the parameter replace client name to true Maca S af Mcllavejor Clelausy 3 i replace client name true The prefix used when generating a FQDN is specified by the generated prefix parameter The default value is myhost To alter its value simply set it to the desired string Macs if Melo clas eS generated prefix another host The suffix used when generating a FQDN or when qualifying a partial name is specified by the qualifying suffix parameter This parameter has no default value thus it is mandatory when DDNS updates are enabled To set its value simply set it to the desired string DECO ce Mlinvejoy eletauss Ss 5 qualifying suffix foo example org Ie Kea Administrator Reference Manual 76 113 When qualifying a partial name kea dhcp6 will construct a name with the format candidate name qualifying suffix where candidate name is the partial name supplied in the REQUEST For example if FODN domain name value was some computer and qualifying suffix example com the generated FQDN would be some computer example com When generating the entire name kea dhcp6 will construct name of the format generated prefix address text qualifying suffix where address text is simply the lease IP address converted to a hyphenated string For example if lease address is 3001 1
109. erefore the Kea DHCPv4 server uses raw sockets by default Raw sockets mean that the incoming packets are received as raw Ethernet frames thus bypassing the whole kernel IP stack including any firewalling rules your kernel may provide If you do not want the server to use raw sockets it is possible to configure the Kea DHCPv4 server to use UDP sockets instead See dhcp socket type described in Section 7 2 3 However using UDP sockets has certain limitations In particular they may not allow for sending responses directly to clients without IPv4 addresses assigned That s ok if all your traffic is coming through relay agents 16 3 Frequently Asked Questions about DHCPv6 16 3 1 Kea DHCPv6 doesn t seem to get incoming traffic checked with tcpdump or other traffic capture software that the incoming traffic is reaching the box What s wrong Please check whether your OS has any IPv6 filtering rules Many operating systems are shipped with firewalls that discard incoming IPv6 traffic by default In particular many Linux distributions do that Please check the output of the following command ip6tables L n One common mistake in this area is to use iptables tool which lists IPv4 firewall rules only Kea Administrator Reference Manual 113 113 Chapter 17 Acknowledgments Kea is primarily designed developed and maintained by Internet Systems Consortium Inc It is an open source project and contributions are welcomed
110. erver will return a status code of 1 error and the text field will contain the error description Kea Administrator Reference Manual 101 113 Chapter 13 Management API A classic approach to daemon configuration assumes that the server s configuration is stored in the configuration files and when the configuration is changed the daemon is restarted This approach has the significant disadvantage of introducing periods of downtime when client traffic is not handled Another risk is that if the new configuration is invalid for whatever reason the server may refuse to start which will further extend the downtime period until the issue is resolved To avoid such problems both DHCPv4 and DHCPv6 servers introduced support for a mechanism that will allow on line recon figuration without requiring server shutdown Both servers can be instructed to open control sockets which is a communication channel The server is able to receive commands on that channel act on them and report back status While the set of commands supported in Kea 0 9 2 is limited the number is expected to grow over time Currently the only supported type of control channel is UNIX stream socket For details how to configure it see Section 7 7 and Section 8 10 It is likely that support for other control channel types will be added in the future 13 1 Data syntax Communication over control channel is conducted using JSON structures If configured Kea will open a
111. eters ip_address IP address on which D2 listens for requests The default is the local loopback interface at address 127 0 0 1 You may specify either an IPv4 or IPv6 address port Port on which D2 listens for requests The default value is 53001 dns_server_timeout The maximum amount of time in milliseconds that D2 will wait for a response from a DNS server to a single DNS update message ncr_protocol Packet format to use when sending requests to D2 Currently only JSON format is supported Other formats may be available in future releases ncr_format Socket protocol to use when sending requests to D2 Currently only UDP is supported TCP may be available in an upcoming release D2 must listen for change requests on a known address and port By default it listens at 127 0 0 1 on port 53001 The following example illustrates how to change D2 s global parameters so it will listen at 192 168 1 10 port 900 HD hie pD in sul ip address 192 168 1 10 port 900 Warning O It is possible for a malicious attacker to send bogus NameChangeRequests to the DHCP DDNS server Addresses other than the IPv4 or IPv6 loopback addresses 127 0 0 1 or 1 should only be used for testing purposes but note that local users may still communicate with the DHCP DDNS server A future version of Kea will implement authentication to guard against such attacks Note If the ip_address and port are changed it will be necessary to
112. ets received This statistic is expected to remain close to zero Its increase pkt4 decline received integer means that a client that leased an address but discovered that the address is currently used by an unknown device in your network Number of DHCPINFORM packets Kea Administrator Reference Manual 53 113 7 9 DHCPv4 Server Limitations These are the current limitations of the DHCPv4 server software Most of them are reflections of the current stage of development and should be treated as not implemented yet rather than actual limitations However some of them are implications of the design choices made Those are clearly marked as such Removal of a subnet during server reconfiguration may cause renumbering of auto generated subnet identifiers as described in section Section 7 2 5 Host reservation static addresses is not supported yet Full featured client classification is not supported yet BOOTP RFC 951 is not supported This is a design choice BOOTP support is not planned On Linux and BSD system families the DHCP messages are sent and received over the raw sockets using LPF and BPF and all packet headers including data link layer IP and UDP headers are created and parsed by Kea rather than the system kernel Currently Kea can only parse the data link layer headers with a format adhering to IEEE 802 3 standard and assumes this data link layer header format for all interfaces
113. f more than one value is allowed Options can also be configured as hexadecimal values If esv format is set to false option data must be specified as a hexadec imal string The following commands configure the domain name servers option for all subnets with the following addresses 192 0 3 1 and 192 0 3 2 Note that csv format is set to false Dhcp4 option darane name domain name servers code 6 space dhcp4 csv format false data CO 00 03 01 CO 00 03 02 Most of the parameters in the option data structure are optional and can be omitted in some circumstances as discussed in the Section 7 2 11 It is possible to specify or override options on a per subnet basis If clients connected to most of your subnets are expected to get the same values of a given option you should use global options you can then override specific values for a small number of subnets On the other hand if you use different values in each subnet it does not make sense to specify global option values Dhcp4 option data rather you should set only subnet specific values Dhcp4 subnet X option datal Y The following commands override the global DNS servers option for a particular subnet setting a single DNS server with address 192 0 2 3 Ms xf subnet4 option data name domain name servers code 6 space dhcp4 csv format true data 192 0 2 3 Kea Administrator Reference Manual
114. ffer in severity some are more important than others and source some are produced by specific components e g hooks It is useful to understand which log messages are needed and which are not and configure your logging appropriately For example debug level messages can be safely ignored in a typical deployment They are however very useful when debugging a problem The logging system in Kea is configured through the Logging structure in your configuration file All daemons e g DHCPv4 and DHCPv6 servers will use the configuration in the Logging structure to see what should be logged and to where This allows for sharing identical logging configuration between daemons 15 1 1 Loggers Within Kea a message is logged through an entity called a logger Different components log messages through different loggers and each logger can be configured independently of one another Some components in particular the DHCP server processes may use multiple loggers to log messages pertaining to different logical functions of the component For example the DHCPv4 server is using one logger for messages pertaining to packet reception and transmission another logger for messages related to lease allocation and so on Some of the libraries used by the Kea servers e g libdhcpsrv or libhooks library use their own loggers Users implementing hooks libraries code attached to the server at runtime are responsible for creating the loggers used by those lib
115. figuration may cause problems e disabled host reservation support is disabled As there are no reservations the server will skip all checks Any reservations defined will be completely ignored As the checks are skipped the server may operate faster in this mode An example configuration that disables reservation looks like follows Kea Administrator Reference Manual 49 113 Dhcp4 subnet4 Sia 12 0 20 2406 reservation mode disabled 7 4 Server Identifier in DHCPv4 The DHCPv4 protocol uses a server identifier to allow clients to discriminate between several servers present on the same link this value is an IPv4 address of the server The server chooses the IPv4 address of the interface on which the message from the client or relay has been received A single server instance will use multiple server identifiers if it is receiving queries on multiple interfaces Currently there is no mechanism to override the default server identifiers by an administrator In the future the configuration mechanism will be used to specify the custom server identifier 7 5 How the DHCPv4 Server Selects a Subnet for the Client The DHCPv4 server differentiates between the directly connected clients clients trying to renew leases and clients sending their messages through relays For the directly connected clients the server will check the configuration for the interface on which the message has been received and if the serve
116. figuration with some of the parameters modified To illustrate this suppose you are using the DHCPv4 server with the root logger kea dhcp4 logging at the INFO level In order to enable DEBUG verbosity for the DHCPv4 packet drops you must create configuration entry for the logger called kea dhcp4 bad packets and specify severity DEBUG for this logger All other configuration parameters may be omited for this logger if the logger should use the default values specified in the root logger s configuration If there are multiple logger specifications in the configuration that might match a particular logger the specification with the more specific logger name takes precedence For example if there are entries for both kea dhcp4 and kea dhcp4 dhcpsrv the DHCP v4 server and all libraries it uses that are not dhcpsrv will log messages according to the configuration in the first entry kea dhcp4 Currently defined loggers are kea dhcp4 this is the root logger for the DHCPv4 server All components used by the DHCPv4 server inherit the settings from this logger if there is no specialized logger provided kea dhcp4 alloc engine this is the logger used by the lease allocation engine which is responsible for managing leases in the lease database i e create modify and remove DHCPv4 leases as a result of processing messages from the clients kea dhcp4 bad packets this is the logger used by the DHCPv4 server d
117. file name used to start the server minus all preceding path and file extension For example given a pathname of usr local etc kea myconf txt the portion used would be myconf If the file already exists and contains the PID of a live process the server will issue a DHCP_DDNS_ALREADY_RUNNING log message and exit Itis possible though unlikely that the file is a remnant of a system crash and the process to which the PID belongs is unrelated to Kea In such a case it would be necessary to manually delete the PID file 9 2 Configuring the DHCP DDNS Server Before starting kea dhcp ddns module for the first time a configuration file needs to be created The following default configu ration is a template that can be customised to your requirements DhcpDdns ip address 127 0 0 1 port 53001 dns _ server _timeout 100 ncr_protocol UDP ncr_format JSON tsig_keys forward_ddns ddns_domains reverse _ddns ddns_domains The configuration can be divided as follows each of which is described in its own section e Global Server Parameters values which control connectivity and global server behavior e TSIG Key Info defines the TSIG keys used for secure traffic with DNS servers e Forward DDNS defines the catalog of Forward DDNS Domains e Reverse DDNS defines the catalog of Forward DDNS Domains Kea Administrator Reference Manual 88 113 9 2 1 Global Server Param
118. from http ftp isc org isc kea using FTP or HTTP 3 4 2 Retrieve from Git Downloading this bleeding edge code is recommended only for developers or advanced users Using development code in a production environment is not recommended Note When building from source code retrieved via Git additional software will be required automake v1 11 or later libtoolize and autoconf 2 59 or later These may need to be installed The latest development code together with temporary experiments and un reviewed code is available via the Kea code revision control system This is powered by Git and all the Kea development is public The leading development is done in the master branch The code can be checked out from git git kea isc org kea git clone git git kea isc org kea The code checked out from the git repository doesn t include the generated configure script Makefile in files nor their related build files They can be created by running autoreconf with the instal1 switch This will run autoconf aclocal libtoolize autoheader automake and related commands Kea Administrator Reference Manual 7 113 3 4 3 Configure before the build Kea uses the GNU Build System to discover build environment details To generate the makefiles using the defaults simply run configure Run configure with the help switch to view the different options Some commonly used options are prefix Define the i
119. further assume that 2001 db8 1 0 5 80 should also be managed by the server It could be written as 2001 db8 1 0 5 to 2001 db8 1 5 ffff ffff ffff but typing so many f s is cumbersome It can be expressed more simply as 2001 db8 1 0 5 80 Both formats are supported by Dhcp6 and can be mixed in the pool list For example one could define the following pools Mao A subnet6 1 Kea Administrator Reference Manual 61 113 subnet 2001 db8 1 64 pools pool 2001 db8 1 1 2001 db8 1 ffff pool 2001 db8 1 05 80 1 The number of pools is not limited but for performance reasons it is recommended to use as few as possible The server may be configured to serve more than one subnet To add a second subnet use a command similar to the following DA subnet6 subnet 2001 db8 1 64 pools pool 2001 db8 1 1 2001 db8 1 ffff subnet 2001 db8 2 64 pools pool 2001 db8 2 64 In this example we allow the server to dynamically assign all addresses available in the whole subnet Although rather wasteful it is certainly a valid configuration to dedicate the whole 64 subnet for that purpose Note that the Kea server does not preallocate the leases so there is no danger in using gigantic address pools When configuring a DHCPV6 server using prefix length notation please pay attention to the boundary values When specifying that the serv
120. g Forward DDNS Domains loaa 90 9 2 3 1 1 Adding Forward DNS Servers a 90 9 24 Reverse DDNS ode ee ae ee e a a a a ae a EN 31 9 2 4 1 Adding Reverse DDNS Domains 0 00000 000000000 91 9 2 4 1 1 Adding Reverse DNS Servers 2 20 0000 0000000 4 92 9 2 5 Example DHCP DDNS Server Configuration 2 000 000 000000004 93 9 3 DHCP DDNS Server Limitations ss 0 0 00 0 0000000000222 bee 94 10 The LFC process 95 10 1 OVERVIEW beth 4 Bede e Seb he RSE SSS GhS4 PASSES EERE SESS DRESSES 95 10 2 Command Line Options 0 0 0002 ee 95 Kea Administrator Reference Manual vii 11 Hooks Libraries 11 1 Introduction 11 2 Configuring Hooks Libraries 12 Statistics 12 1 Statistics OVverview 4 da 24 ae eee ak de ee bol de wae ee ee bt ba eee ee eA ee ee do 12 2 Statistics Lifecycle comas SE Ea SESE grea RAGE Bae Re eee Pace haan 4 Bags a ok 12 3 Commands for Manipulating Statistics 2 ee 12 3 1 statistic 12 3 2 statistic reset command pe sers puda ea aa ke eaa a a e a e a k a s 12 3 3 statistic remove command ooo e a 12 3 4 statistic get allcommand oa a 12 3 5 statistic reset all command ooa a e 12 3 6 statistic remove all command ooa a 13 Management API 13 1 Data syntax 13 2 Using control channels lt o eros gpa Be E A ee RA RA e a OR 13 3 Commands supported by both DHCPv4 and DHCPv6 servers e 13 3 1 list cc
121. he Se 55 8 2 2 Lease Storage 2 ss aen ae Pe ba Gabe eS eh CaaS ORE a Ca EES 57 8 2 2 1 Memfile Basic Storage for Leases o 34 8 2 2 2 Database Configuration 58 8 2 3 Interface s lectionl s ias oe RR ER eA OR A Re be a we ee 58 8 2 4 IPv6 Subnet Identifier 20 0000 0 0000000000000 000000000004 59 2 5 Unicasttiratic support e oce 6 4 wah eee o Bek ele wy Ee ee ee 8S 60 8 2 6 Subnetand Address POOl vos 2 ee 3 edd ba ee RS EES DE e Ra E ESS Sa Pewee eee eG ES 60 8 2 7 Subnet and Prefix Delegation Pools 0 0 0 0 0 2 ee eee 61 8 2 8 Standard DHCPv6 Options 62 8 29 Custom DHCPVG 0ptions sgae sup ears Sip he ee RE ESS Shaw EY EYES Se Pewee ee ee ea 63 8 2 10 DHCPv6 vendor specific Options 66 8 2 11 Nested DHCPv6 options custom option spaces e 67 8 2 12 Unspecified parameters for DHCPv6 option configuration e 68 8 2 13 IPyYO Subnet Selection lt s sos sey n peoa RE Ae a a ee 69 8 2 14 Rapid Commit sc meena e bea a ee a ee Ba eA ee ee A a e a 69 Kea Administrator Reference Manual vi 82 15 DHCPV6 Relays a4 4454 see pe di as A eee eS oS 70 8 2 16 Relay Supplied Options 2 2 2 0 0 000 000 a 70 8 2 17 Client Classification in DHCOPV6 2 0 0 0 0000 2 eee eee 71 8 2 18 Limiting access to IPv6 subnet to certain classes 2 ee ee 71 8 2 19 Configuring DHCPv6 for DDNS p ea e e E R a a a E E E E E T2 8 2 19 1 DHCP DDNS Server Connectivity
122. he source directory and run the configure script cd kea 0 9 2 configure your extra parameters Build it S make Install it by default the installation prefix is usr local so you likely need root privileges for that step make install Edit the configuration file which by default is installed in kea install dir etc kea kea conf and contains configuration for all Kea services Configuration choices for DHCPv4 and DHCPV6 services are described in Section 7 2 and Section 8 2 respectively In order to start the DHCPv4 server in background run the following command as root keactrl start s dhcp4 Or run the following command to start DHCPvV6 server instead keactrl start s dhcp6 Note that it is also possible to start both servers simultaneously keactrl start Kea Administrator Reference Manual 4 113 9 Verify that Kea server s are running keactrl status If the server status is inactive may indicate a configuration error Please check a log file by default located in kea install var kea kea 1og for the details of the error 10 If the server has been started sucessfully test that it is responding to DHCP queries and that the client receives a configu ration from the server for example use the ISC DHCP client 11 Stop running server s keactrl stop For more system specific installation procedures you may want to visit System specific notes available on
123. herefore it is recommended that the Ifc interval value is selected in a way that would allow for completing the cleanup before the new cleanup is triggered The LFC is performed by a separate process in background to avoid performance impact on the server process In order to avoid the conflicts between the two processes both using the same lease files the LFC process operates on the copy of the original lease file rather than on the lease file used by the server to record lease updates There are also other files being created as a side effect of the lease file cleanup The detailed description of the LFC is located on the Kea wiki http kea isc org wiki LFCDesign 8 2 2 2 Database Configuration Note Database access information must be configured for the DHCPV6 server even if it has already been configured for the DHCPv4 server The servers store their information independently so each server can use a separate database or both servers can use the same database Database configuration is controlled through the Dhcp6 lease database parameters The type of the database must be set to mysql or postgresql e g Dhcp6 lease database type mysql Next the name of the database is to hold the leases must be set this is the name used when the lease database was created see Section 4 3 2 1 or Section 4 3 3 1 Dhcp6 lease database name database name If the database is locat
124. i x previous fil i Colon rile O QUEUE lea lt gt 16 aa lacas The argument 4 or 6 selects the protocol version of the lease files The c argument specifies the configuration file This is required but not currently used by the process The p argument specifies the PID file When the kea Ife process starts it attempts to determine if another instance of the process is already running by examining the pid file If one is already running the new process is terminated If one isn t running it writes its pid into the pid file The other filenames specify where the kea Ifc process should look for input write its output and use for bookkeeping previous When kea lfe starts this is the result of any previous run of kea Ifc When kea Ife finishes it is the result of this run If kea lfc is interrupted before compelting this file may not exist input Before the DHCP server invokes kea lfc it will move the current lease file here and then call kea Ifc with this file output The temporary file kea Ifc should use to write the leases Upon completion of writing this this file it will be moved to the finish file see below finish Another temporary file kea Ifc uses for bookkeeping When kea Ife completes writing the outputfile it moves it to this file name After kea Ife finishes deleting the other files previous and input it moves this file to previous lease file By moving the files in this fashion the kea lfc and the DHCP serv
125. ient update true The third row in the table above describes the case in which the client requests that no DNS updates be done The parameter override no update can be used to instruct the server to disregard the client s wishes When this parameter is true kea dhcp6 will generate DDNS update requests to kea dhcp ddns even if the client requests no updates be done The N S O flags in the server s response to the client will be 0 1 1 To override client delegation issue the following commands Kea Administrator Reference Manual 75 113 acne xf Welavejo Cloins a override no update true 8 2 19 3 kea dhcp6 name generation for DDNS update requests Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected kea dhcp6 can be configured to supply a portion or all of that name based upon what it receives from the client in the DHCP REQUEST The rules for determining the FQDN option are as follows 1 If configured to do so ignore the REQUEST contents and generate a FQDN using a configurable prefix and suffix 2 Otherwise using the domain name value from the client FQDN option as the candidate name a If the candidate name is a fully qualified domain name then use it b If the candidate name is a partial i e unqualified name then add a configurable suffix to the name and use the result as the FQDN c If the candidate name is a empty then gen
126. ill have code 100 and will convey a single unsigned 32 bit integer value We can define such an option by using the following commands Macas i Hoprilon aci name foo code 100 type uint32 array false record types space dhcp6 encapsulate Kea Administrator Reference Manual 64 113 Name Code Type Array preference 7 uint8 false vendor opts 17 uint32 false sip server dns 21 fqdn true sip server addr 22 ipv6 address true dns servers 23 ipv6 address true domain search 24 fqdn true nis servers 27 ipv6 address true nisp servers 28 ipv6 address true nis domain name 29 fqdn true nisp domain name 30 fqdn true sntp servers 31 ipv6 address true information refresh time 32 uint32 false bcmcs server dns 33 fqdn true bcemcs server addr 34 ipv6 address true geoconf civic 36 record false remote id 37 record false subscriber id 38 binary false client fqdn 39 record false pana agent 40 ipv6 address true new posix timezone 41 string false new tzdb timezone 42 string false ero 43 uint16 true lq query 44 record false client data 45 empty false clt time 46 uint32 false lq relay data 47 record false lq client link 48 ipv6 address true erp local domain name 65 fqdn false rsoo 66 empty false client linklayer addr 79 binary false Table 8 1 List of standard DHCPv6 options Kea Administrato
127. inary format represented as a string of hexadecimal digits Note that not specifying this parameter doesn t imply that it defaults to a fixed value but the configuration data interpretation also depends on the presence of the option definition An administrator must be aware if the definition for the particular option exists when this parameter is not specified It is generally recommended to not specify this parameter only for the options for which the definition exists e g standard options Setting csv format to an explicit value will cause the server to strictly check the format of the option data specified 8 2 13 IPv6 Subnet Selection The DHCPv6 server may receive requests from local connected to the same subnet as the server and remote connecting via relays clients As the server may have many subnet configurations defined it must select an appropriate subnet for a given request The server can not assume which of the configured subnets are local In IPv4 it is possible as there is a reasonable expectation that the server will have a global IPv4 address configured on the interface and can use that information to detect whether a subnet is local or not That assumption is not true in IPv6 the DHCPV6 server must be able to operate while only having link local addresses Therefore an optional interface parameter is available within a subnet definition to designate that a given subnet is local i e reachable directly over the specified
128. ions Numbers in the first column are added for easier reference and will not appear on screen Options specified in this way are considered global and apply to all configured subnets DEce ore toperon data al name dns servers code 23 space dhcp6 csv format true data 2001 db8 cafe 2001 db8 babe The option data gt line creates a new entry in the option data table This table contains information on all global options that the server is supposed to configure in all subnets The name line specifies the option name For a complete list of currently supported names see Table 8 1 The next line specifies the option code which must match one of the values from that list The line beginning with space specifies the option space which must always be set to dhcp6 as these are standard DHCPv6 options For other name spaces including custom option spaces see Section 8 2 11 The next line specifies the format in which the data will be entered use of CSV comma separated values is recommended The data line gives the actual value to be sent to clients Data is specified as normal text with values separated by commas if more than one value is allowed Options can also be configured as hexadecimal values If csv format is set to false the option data must be specified as a string of hexadecimal numbers The following commands configure the DNS SERVERS option for all subnets with the following addresses 2001 db8 1 cafe
129. le e g at the server startup it assumes that the latest lease entry for the client is the valid one The previous entries are discarded This means that the server can re construct the accurate information about the leases even though there may be many lease entries for each client However storing many entries for each client results in bloated lease file and impairs the performance of the servers startup and reconfiguration as it needs to process larger number of lease entries Kea Administrator Reference Manual 58 113 The lease file cleanup removes all previous entries for each client and leaves only the latest ones The interval at which the cleanup is performed is configurable and it should be selected according to the frequency of lease renewals initiated by the clients The more frequent renewals are the lesser value of the Ifc interval should be Note however that the LFC takes time and thus it is possible although unlikely that new cleanup is started while the previous cleanup instance is still running if the Ifc interval is too short The server would recover from this by skipping the new cleanup when it detects that the previous cleanup is still in progress But this implies that the actual cleanups will be triggered more rarely than configured Moreover triggering a new cleanup adds an overhead to the server which will not be able to respond to new requests for a short period of time when the new cleanup process is spawned T
130. ll be assumed to belong to another client and the new lease will be allocated 7 3 Host reservation in DHCPv4 There are many cases where it is useful to provide a configuration on a per host basis The most obvious one is to reserve specific static address for exclusive use by a given client host returning client will receive the same address from the server every time and other clients will generally not receive that address Note that there may be cases when the new reservation has been made for the client for the address being currently in use by another client We call this situation a conflict The conflicts get resolved automatically over time as described in the subsequent sections Once conflict is resolved the client will keep receiving the reserved configuration when it renews Another example when the host reservations are applicable is when a host that has specific requirements e g a printer that needs additional DHCP options Yet another possible use case is to define unique names for hosts Although not all of the presented use cases are implemented yet Kea software will support them in the near future Hosts reservations are defined as parameters for each subnet Each host has to be identified by its hardware MAC address There is an optional reservations array in the Subnet4 element Each element in that array is a structure that holds information about reservrations for a single host In particular such a structure has to hav
131. lowest e out of pool allows only out of pool host reservations With this setting in place the server may assume that all host reserva tions are for addresses that do not belong to the dynamic pool Therefore it can skip the reservation checks when dealing with in pool addresses thus improving performance Do not use this mode if any of your reservations use in pool address Caution is advised when using this setting Kea 0 9 2 does not sanity check the reservations against reservation mode Misconfiguration may cause problems e disabled host reservation support is disabled As there are no reservations the server will skip all checks Any reservations defined will be completely ignored As the checks are skipped the server may operate faster in this mode An example configuration that disables reservation looks like follows Macas f subneto WS TiO Mcien s YOOL clogs Lei GAW reservation mode disabled 8 4 Server Identifier in DHCPv6 The DHCPv6 protocol uses a server identifier also known as a DUID for clients to be able to discriminate between several servers present on the same link There are several types of DUIDs defined but RFC 3315 instructs servers to use DUID LLT if possible This format consists of a link layer MAC address and a timestamp When started for the first time the DHCPv6 server will automatically generate such a DUID and store the chosen value to a file That file is read by the server an
132. m of NCRs Carrying out the actual DNS updates and dealing with such things as conflict resolution are the purview of D2 Chapter 9 This section describes when kea dhcp6 will generate NCRs and the configuration parameters that can be used to influence this decision It assumes that the enable updates parameter is true Kea Administrator Reference Manual 74 113 Note Currently the interface between kea dhcp6 and D2 only supports requests which update DNS entries for a single IP address If a lease grants more than one address kea dhcp6 will create the DDNS update request for only the first of these addresses Support for multiple address mappings may be provided in a future release In general kea dhcp6 will generate DDNS update requests when 1 A new lease is granted in response to a DHCP REQUEST 2 An existing lease is renewed but the FQDN associated with it has changed 3 An existing lease is released in response to a DHCP RELEASE In the second case lease renewal two DDNS requests will be issued one request to remove entries for the previous FQDN and a second request to add entries for the new FQDN In the last case a lease release a single DDNS request to remove its entries will be made The decision making involved when granting a new lease is more involved and is discussed next kea dhcp6 will generate a DDNS update request only if the DHCP REQUEST contains the FQDN option code 39 By default kea dhcp6 will respec
133. meter replace client name to true as follows Dhcep4 sanepa danS nea replace client name true The prefix used in the generation of a FQDN is specified by the generated prefix parameter The default value is myhost To alter its value simply set it to the desired string Kea Administrator Reference Manual 43 113 Dhcp4 dhep Celis esau generated prefix another host The suffix used when generating a FQDN or when qualifying a partial name is specified by the qualifying suffix parameter This parameter has no default value thus it is mandatory when DDNS updates are enabled To set its value simply set it to the desired string Dhcep4 elos i qualifying suffix foo example org When generating a name kea dhcp4 will construct name of the format generated prefix address text qualifying suffix where address text is simply the lease IP address converted to a hyphenated string For example if the lease address is 172 16 1 10 the qualifying suffix example com and the default value is used for generated prefix the generated FQDN would be myhost 172 16 1 10 example com 7 2 15 Next Server siaddr In some cases clients want to obtain configuration from the TFTP server Although there is a dedicated option for it some devices may use the siaddr field in the DHCPv4 packet for that purpose That specific field can be configured using next server directive It is possible to define i
134. n Gatan name suboptl code 1 space isc data 2001 db8 abcd name subopt2 code 2 space isc data Hello world name container code 102 space dhcp6 Note that it is possible to create an option which carries some data in addition to the sub options defined in the encapsulated option space For example if the container option from the previous example was required to carry an uint16 value as well as the sub options the type value would have to be set to uint16 in the option definition Such an option would then have the following data structure DHCP header uint16 value sub options The value specified with the data parameter which should be a valid integer enclosed in quotes e g 123 would then be assigned to the uint16 field in the container option 8 2 12 Unspecified parameters for DHCPv6 option configuration In many cases it is not required to specify all parameters for an option configuration and the default values can be used However 1t is important to understand the implications of not specifing some of them as it may result in configuration errors The list below explains the behavior of the server when a particular parameter is not explicitly specified e name the server requires an option name or option code to identify an option If this parameter is unspecified the option code must be specified e code the server requires an option n
135. n and is configured to insert it This method is useless for directly connected clients This parameter can also be specified as rfc6939 which is an alias for client link addr option remote id RFC 4649 defines remote id option that is inserted by a relay agent Depending on the relay agent configuration the inserted option may convey client s MAC address information This parameter can also be specified as rfc4649 which is an alias for remote id subscriber id Another option that is somewhat similar to the previous one is subscriber id defined in RFC 4580 It is too inserted by a relay agent that is configured to insert it This parameter can also be specified as rfc4580 which is an alias for subscriber id This method is currently not implemented Kea Administrator Reference Manual 83 113 docsis cmts Yet another possible source of MAC address information are DOCSIS options inserted by a CMTS that acts as a DHCPv6 relay agent in cable networks This method attempts to extract MAC address information from suboption 1026 cm mac of the vendor specific option with vendor id 4491 This vendor option is extracted from the relay forward message not the original client s message docsis modem Yet another possible source of MAC address information are DOCSIS options inserted by the cable modem itself This method attempts to extract MAC address information from suboption 36 device id of the vendor specific option with vendor id 4
136. n changed Let s first consider the case when the client obtains the lease when the match client id is set to true The server will store the lease information including client identifier if supplied and chaddr in the lease database When the setting is changed and the client renews the lease the server will determine that it should use the chaddr to search for the existing lease If the client hasn t changed its MAC address the server should successfully find the existing lease The client identifier associated with the returned lease is ignored and the client is allowed to use this lease When the lease is renewed only the chaddr is recorded for this lease according to the new server setting In the second case the client has the lease with only a chaddr value recorded When the setting is changed to match client id set to true the server will first try to use the client identifier to find the existing client s lease This will return no results because the client identifier was not recorded for this lease The server will then use the chaddr and the lease will be found If the lease appears to have no client identifier recorded the server will assume that this lease belongs to the client and that it was created with the previous setting of the match client id However if the lease contains client identifier which is different from the client identifier used by the client the lease wi
137. nd plain text formats along with other documents for Kea can be found at http kea isc org docs Kea Administrator Reference Manual 1 113 Chapter 1 Introduction Kea is the next generation of DHCP software developed by ISC It supports both DHCPv4 and DHCPv6 protocols along with their extensions e g prefix delegation and dynamic updates to DNS Kea was initially developed as a part of the BIND 10 framework In early 2014 ISC made the decision to discontinue active development of BIND 10 and continue development of Kea as standalone DHCP software This guide covers Kea version 0 9 2 1 1 Supported Platforms Kea is officially supported on RedHat Enterprise Linux CentOS Fedora and FreeBSD systems It is also likely to work on many other platforms builds have been tested on in no particular order Debian GNU Linux 6 and unstable Ubuntu 9 10 NetBSD 5 Solaris 10 and 11 FreeBSD 7 and 8 CentOS Linux 5 3 MacOS 10 6 and 10 7 and OpenBSD 5 1 Non supported systems especially non Linux are likely to have issues with directly connected DHCPV4 clients There are currently no plans to port Kea to Windows platforms 1 2 Required Software at Run time Running Kea uses various extra software which may not be provided in the default installation of some operating systems nor in the standard package collections You may need to install this required software separately For the build requirements also see Section 3 3 Kea supp
138. nfiguration MD tf Ichaveio Clclos i override no update true kea dhcp4 will always generate DDNS update requests if the client request only contains the Host Name option In addition it will include an FQDN option in the response to the client with the FODN N S O flags set to 0 1 0 respectively The domain name portion of the FQDN option will be the name submitted to D2 in the DDNS update request 7 2 14 3 kea dhcp4 name generation for DDNS update requests Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected kea dhcp4 can be configured to supply a portion or all of that name based upon what it receives from the client in the DHCP REQUEST The rules for determining the FQDN option are as follows 1 If configured to do so ignore the DHCPREQUEST contents and generate a FQDN using a configurable prefix and suffix 2 If the DHCPREQUEST contains the client FQDN option the candidate name is taken from there otherwise it is taken from the Host Name option The candidate name may then be modified a If the candidate name is a fully qualified domain name use it b If the candidate name is a partial i e unqualified name then add a configurable suffix to the name and use the result as the FQDN c If the candidate name is a empty generate a FQDN using a configurable prefix and suffix To instruct kea dhcp4 to always generate the FQDN for a client set the para
139. nfiguration file Since the DHCPv4 server opens privileged ports it requires root access Make sure you run this daemon as root During startup the server will attempt to create a PID file of the form localstatedir conf name kea dhcp4 pid where e localstatedir The value as passed into the build configure script It defaults defaults to usr local var Note that this value may be overridden at run time by setting the environment variable KEA_PIDFILE_DIR This is intended primarily for testing purposes Kea Administrator Reference Manual 22 113 e conf name The confguration file name used to start the server minus all preceding path and file extension For example given a pathname of usr local etc kea myconf txt the portion used would be myconf If the file already exists and contains the PID of a live process the server will issue a DHCP4_ALREADY RUNNING log message and exit It is possible though unlikely that the file is a remnant of a system crash and the process to which the PID belongs is unrelated to Kea In such a case it would be necessary to manually delete the PID file 7 2 DHCPv4 Server Configuration 7 2 1 Introduction This section explains how to configure the DHCPv4 server using the Kea configuration backend Kea configuration using any other backends is outside of scope of this document Before DHCPv4 is started its configuration file has to be created The basic configuration is as follows
140. nfigured to generate requests to the DHCP DDNS server referred to here as D2 to update DNS entries These requests are known as NameChangeRequests or NCRs Each NCR contains the following information 1 Whether it is a request to add update or remove DNS entries 2 Whether the change requests forward DNS updates A records reverse DNS updates PTR records or both 3 The FQDN lease address and DHCID The parameters for controlling the generation of NCRs for submission to D2 are contained in the dhep ddns section of the kea dhcp4 server configuration The mandatory parameters for the DHCP DDNS configuration are enable updates which is unconditionally required and qualifying suffix which has no default value and is required when enable updates is set to true The two disabled and enabled minimal DHCP DDNS configurations are Mas i Melmcio cems Ys enable updates false and for example Kea Administrator Reference Manual 40 113 Une Al NEP AAA SU enable updates true qualifying suffix example The default values for the dhcp ddns section are as follows server ip 127 0 0 1 server port 53001 sender ip sender port 0 max queue size 1024 ner protocol UDP ner format JSON override no update false override client update false replace client name false men generated prefix myhost 7 2 14 1 DHCP DDNS Server Connectivity In order for NCRs to r
141. ng to the client even if the current chaddr and the chaddr associated with the lease do not match This facilitates the scenario when the network card on the client system has been replaced and thus the new MAC address appears in the messages sent by the DHCP client If the server fails to find the lease using the client identifier it will perform another lookup using the chaddr If this lookup returns no result the client is considered as not having a lease and the new lease will be created A common problem reported by network operators is that bogus client implementations do not use stable client identifiers such as generating a new client identifier each time the client connects to the network Another well known case is when the client changes its client identifier during the multi stage boot process PXE In such cases the MAC address of the client s interface remains stable and using chaddr field to identify the client guarantees that the particular system is considered to be the same client even though its client identifier changes To address this problem Kea includes a configuration option which enables client identification using chaddr only by instructing the server to disregard server to ignore the client identifier during lease lookups and allocations for a particular subnet Consider the following simplified server configuration Dhcp4 Kea Administrator Reference Manual 45
142. ng traffic and extract MAC hardware address information This is currently not implemented for DHCPv6 and this value has no effect duid DHCPv6 uses DUID identifiers instead of MAC addresses There are currently four DUID types defined with two of them DUID LLT which is the default one and DUID LL convey MAC address information Although RFC3315 forbids it it is possible to parse those DUIDs and extract necessary information from them This method is not completely reliable as clients may use other DUID types namely DUID EN or DUID UUID ipv6 link local Another possible aquisition method comes from the source IPv6 address In typical usage clients are sending their packets from IPv6 link local addresses There s a good chance that those addresses are based on EUI 64 which contains MAC address This method is not completely reliable as clients may use other link local address types In particular privacy extensions defined in RFC4941 do not use MAC addresses Also note that successful extraction requires that the address s u bit must be set to 1 and its g bit set to 0 indicating that it is an interface identifier as per RFC 2373 section 2 5 1 client link addr option One extension defined to alleviate missing MAC issues is client link layer address option defined in RFC 6939 This is an option that is inserted by a relay and contains information about client s MAC address This method requires a relay agent that supports the optio
143. nstallation location the default is usr local with boost include Define the path to find the Boost headers with botan config To specific the path to the botan config script to build with Botan for the crypto code with gtest Enable the building of the C Unit Tests using the Google Test framework Optionally this can define the path to the gtest header files and library If the framework is not already installed on your system it can be downloaded from https code google com p googletest with log4cplus Define the path to find the Log4cplus headers and libraries with openssl Replace Botan by OpenSSL for the crypto library The default is to try to find a working Botan then OpenSSL only if Botan is not found without werror Disable the default use of the Werror compiler flag so that compiler warnings do not result in build failures Note For additional instructions concerning the building and installation of Kea for various databases see Section 3 6 For additional instructions concerning the configuration backends see Section 3 5 For example the following command configures Kea to find the Boost headers in usr pkg include specifies that PostgreSQL support should be enabled and sets the installation location to opt kea configure with boost include usr pkg include with dhcp pgsgl usr local bin pg_config prefix opt kea If the configure fails it may be due to missing or old dep
144. ntly Asked Questions about DHCPv4 2 2 2 0 000000022 eee ee 112 16 2 1 I set up a firewall but the Kea server still receives the traffic Why o o o 112 16 3 Frequently Asked Questions about DHCPv6 2 0 0 0 0 02 ee eee ee 112 16 3 1 Kea DHCPv6 doesn t seem to get incoming traffic I checked with tcpdump or other traffic capture software that the incoming traffic is reaching the box What s wrong o 112 17 Acknowledgments 113 Kea Administrator Reference Manual ix List of Tables 7 1 72 7 3 7 4 7 5 8 1 8 2 8 3 9 1 9 2 9 3 List of standard DHCPv4 Options 32 List of standard DHCPv4 options continued 2 2 a 33 List of standard DHCP option types a 33 Default FQDN Flag Behavior ee 41 DHCPyA Statistics 6 3 ci Bee eee a BB re A A A edie E 52 List of standard DHCPv6 options 64 Default FQDN Flag Behavior 74 DHCPv6 Statistics p s scora pea ae ba a A RA ES a ee Le he eS 84 Ourexample network eur e see AR eee Yo ea Se YR ee ws E 93 Forward DDNS Domains Needed 20 00 0000 000022 ne rapea 93 Reverse DDNS Domains Needed 2 0 a ee 94 Abstract Kea is an open source implementation of the Dynamic Host Configuration Protocol DHCP servers developed and maintained by Internet Systems Consortium ISC This is the reference guide for Kea version 0 9 2 The most up to date version of this document in PDF HTML a
145. o a query it needs to check whether there is a lease for a given address being considered for allocation or renewal The server that also supports host reservation has to perform additional checks not only if the address is currently used if there is a lease for it but also whether the address could be used by someone else if there is a reservation for it That additional check incurs performance penalty 7 3 1 Address reservation types In a typical scenario there is an IPv4 subnet defined e g 192 0 2 0 24 with certain part of it dedicated for dynamic allocation by the DHCPv4 server That dynamic part is referred to as a dynamic pool or simply a pool In principle the host reservation can reserve any address that belongs to the subnet The reservations that specify addresses that belong to configured pools are called in pool reservations In contrast those that do not belong to dynamic pools are called out of pool reservations There is no formal difference in the reservation syntax As of 0 9 1 both reservation types are handled uniformly However upcoming releases may offer improved performance if there are only out of pool reservations as the server will be able to skip reservation checks when dealing with existing leases Therefore system administrators are encouraged to use out of pool reservations if possible 7 3 2 Conflicts in DHCPv4 reservations As the reservations and lease information are stored separately conflicts may arise
146. ommandscommand 0 a 13 3 2 shutdowncommand s so ss 2 0 00 ee anp kE a S 14 libdhcp library 14 1 Interface detection and Socket handling 2 0 00 0000000000 0 000 15 Logging 15 1 Logging Configuration s csd 2 E n E E A E E E E AAE e I5 LOG StS oe ase a a ee a e Ra a wi e e al ee IWS name SUM ses pea 54a be Bo Ba RE OR ee Se eR ee 15 1 132 seventy string 0 b4 behest er eGe ee aed Shee bh 15 1 1 3 output_options list 2 a 15 1 1 4 debuglevel Integer lt e ss ee ee ee ee ee 15 1 2 Output Options 2 2 546 246 44 254 ees hd be Shee ah HHS eEES SE be ESAS SES 15 1 2 1 destination SAD 151 22 QUtput ste e s 55 seb 4G en he aes deen eres ph a 15 1 2 2 1 maxsize Gnteger lt s sig 8 bk a a ee es Oe SE a a 15 1 2 2 2 maxver tego 15 1 3 Example Logger Configurations ooa ee 15 2 Logging Message Format ceeredreapt esu d npa pE reno nearring nep 15 3 Logging During Kea Startup seora onpa a a ani e e Aea ES Se eS Oe we bk EAE SES y e 96 96 96 98 98 98 09 99 99 99 100 100 100 101 101 102 102 102 102 103 103 Kea Administrator Reference Manual viii 16 Frequently Asked Questions 111 16 1 Generic Frequently Asked Questions 2 2 a 111 16 1 1 Where did the Kea name came from 2 20 0000 02 a 111 16 1 2 Feature X is not supported yet When if will it be available o oo UN 16 2 Freque
147. on process and their initial packets reached your server Number of ADVERTISE packets received Advertise packets are sent by the server and the server is never expected to receive them A non zero value of this statistic indicates an error ocurring in the network One likely cause would be a misbehaving relay agent that incorrectly forwards ADVERTISE messages towards the server rather back to the clients Number of REQUEST packets received This statistic is expected to grow Its increase means that clients pkt6 request received integer that just booted received the server s response ADVERTISE accepted it and are now requesting an address REQUEST Number of REPLY packets received This statistic is expected to remain zero at all times as REPLY packets are sent by the server and the server is never expected to receive them A non zero value indicates an error One likely cause would be a misbehaving relay agent that incorrectly forwards REPLY messages towards the server rather back to the clients Number of RENEW packets received This statistic is expected to grow Its pkt6 renew received integer increase means that clients received their addresses and prefixes and are trying to renew them Number of REBIND packets received A non zero value indicates that clients didn t receive responses to their RENEW messages regular lease pnkt6 rebind received integer renewal mechanism and are pkt6 received integer
148. one of them is removed the subnet identifiers may be renumbered For example if there are four subnets and the third is removed the last subnet will be assigned the identifier that the third subnet had before removal As a result the leases stored in the lease database for subnet 3 are now associated with subnet 4 something that may have unexpected consequences It is planned to implement a mechanism to preserve auto generated subnet ids in a future version of Kea However the only remedy for this issue at present is to manually specify a unique identifier for each subnet The following configuration will assign the specified subnet identifier to the newly configured subnet ones subnet4 Stoner WILD 2 0 7 24 id 1024 This identifier will not change for this subnet unless the id parameter is removed or set to 0 The value of 0 forces auto generation of the subnet identifier 7 2 6 Configuration of IPv4 Address Pools The essential role of DHCPv4 server is address assignment The server has to be configured with at least one subnet and one pool of dynamic addresses to be managed For example assume that the server is connected to a network segment that uses the 192 0 2 0 24 prefix The Administrator of that network has decided that addresses from range 192 0 2 10 to 192 0 2 20 are going to be managed by the Dhcp4 server Such a configuration can be achieved in the following way ao Al subnet4 subnet 192 0 2 0 24
149. oon Currently the server checks whether an incoming packet includes the vendor class identifier option 60 If it does the content of that option is prepended with VEN DOR_CLASS_ then it is interpreted as a class For example modern cable modems will send this option with value docsis3 0 and as a result the packet will belong to class VENDOR_CLASS_docsis3 0 It is envisaged that the client classification will be used for changing the behavior of almost any part of the DHCP message processing including assigning leases from different pools assigning different options or different values of the same options etc For now there are only two mechanisms that are taking advantage of client classification specific processing for cable modems and subnet selection For clients that belong to the VENDOR_CLASS_docsis3 0 class the siaddr field is set to the value of next server if specified in a subnet If there is a boot file name option specified its value is also set in the file field in the DHCPv4 packet For eRouter1 0 Kea Administrator Reference Manual 39 113 class the siaddr is always set to 0 0 0 0 That capability is expected to be moved to an external hook library that will be dedicated to cable modems Kea can be instructed to limit access to given subnets based on class information This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets Th
150. ord to indicate that the option contains multiple values of different types These types are given as a comma separated list in the record types field and should be those listed in Table 7 3 The values of the option are set as follows Dhcp4 Hoperon dacro e name bar 5 space dhcp4 code 223 csv format true data 192 0 2 100 123 true Hello World csv format is set to true to indicate that the data field comprises a command separated list of values The values in the data must correspond to the types set in the record types field of the option definition Note In the general case boolean values are specified as true or false without quotes Some specific boolean parameters may accept also true false 0 1 0 and 1 Future Kea versions will accept all those values for all boolean parameters 7 2 9 DHCPv4 Vendor Specific Options Currently there are two option spaces defined for the DHCPv4 daemon dhcp4 for the top level DHCPv4 options and vendor encapsulated options space which is empty by default but options can be defined in it Those options will be carried in the Vendor Specific Information option code 43 The following examples show how to define an option foo with code 1 that consists of an IPv4 address an unsigned 16 bit integer and a string The foo option is conveyed in a Vendor Specific Information option The first step is to define the format of the option
151. orts two crypto libraries Botan and OpenSSL Only one of them is required to be installed during compilation Kea uses the Botan crypto library for C http botan randombit net version 1 8 or later As an alternative to Botan Kea can use the OpenSSL crypto library http www openssl org It requires a version with SHA 2 support Kea uses the log4cplus C logging library http log4cplus sourceforge net It requires at least log4cplus version 1 0 3 In order to store lease information in a MySQL database Kea requires MySQL headers and libraries This is an optional dependency in that Kea can be built without MySQL support In order to store lease information in a PostgreSQL database Kea requires PostgreSQL headers and libraries This is an optional dependency in that Kea can be built without PostgreSQL support Kea Administrator Reference Manual 2 113 1 3 Kea Software Kea is modular Part of this modularity is accomplished using multiple cooperating processes which together provide the server functionality The following software is included with Kea keactrl Tool to start stop reconfigure and report status for the Kea servers kea dhcp4 DHCPv4 server process This process responds to DHCPv4 queries from clients kea dhcp6 DHCPv6 server process This process responds to DHCPv6 queries from clients kea dhcp ddns DHCP DDNS process This process acts as an intermediary between the DHCP servers and
152. oving the last subnet from the list However removing non last e g removing subnet 1 2 or 3 if there are 4 subnets configured will cause issues The problem is caused by simplistic subnet id assignment The subnets are always numbered starting from 1 That subnet id is then used in leases that are stored in the lease database Removing non last subnet will cause the configuration information to mismatch data in the lease database It is possible to manually update subnet id fields in MySQL or PostgreSQL database but it is awkward and error prone process A better reconfiguration support is planned The server will allocate renew or rebind a maximum of one lease for a particular IA option IA_NA or IA_PD sent by a client RFC 3315 and RFC 3633 allow for multiple addresses or prefixes to be allocated for a single IA Temporary addresses are not supported Duplication report DECLINE and client reconfiguration RECONFIGURE are not yet supported The server doesn t act upon expired leases In particular when a lease expires the server doesn t request removal of the DNS records associated with it Kea Administrator Reference Manual 86 113 Chapter 9 The DHCP DDNS Server The DHCP DDNS Server kea dhcp ddns known informally as D2 conducts the client side of the DDNS protocol defined in RFC 2136 on behalf of the DHCPv4 and DHCPV6 servers kea dhcp4 and kea dhcp6 respectively The DHCP servers construct DDNS update requests kno
153. owing examples show how to define an option foo with code 1 that consists of an IPv6 address an unsigned 16 bit integer and a string The foo option is conveyed in a Vendor specific Information option This option comprises a single uint32 value that is set to 12345 The sub option foo follows the data field holding this value MIDS S sf MOPpuION ASA name foo code 1 space vendor opts space type record array false record types ipv6 address uint16 string encapsulate Note that the option space is set to vendor opts space Once the option format is defined the next step is to define actual values for that option Mao of LOpiELOM Catectecmal name foo space vendor opts space data 2001 db8 1 10 123 Hello World We should also define a value enterprise number for the Vendor specific Information option that conveys our option foo DNC S yf WU OPiEdO Me Care cuca name vendor opts data 12345 Kea Administrator Reference Manual 67 113 Alternatively the option can be specified using its code Whew cre option darani a codec data 12345 8 2 11 Nested DHCPv6 options custom option spaces It is sometimes useful to define completely new option spaces This is useful if the user wants his new option to convey sub options that use a separate numbering scheme for example sub options with codes 1 and 2 Those option code
154. pools assigning different option or different values of the same options etc For now there is only one mechanism that is taking advantage of client classification subnet selection Kea can be instructed to limit access to given subnets based on class information This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets The primary use case for such a scenario are cable networks There are two classes of devices the cable modem itself which should be handed a lease from subnet A and all other devices behind modems that should get a lease from subnet B That segregation is essential to prevent overly curious users from playing with their cable modems For details on how to set up class restrictions on subnets see Section 8 2 18 8 2 18 Limiting access to IPv6 subnet to certain classes In certain cases it beneficial to restrict access to certain subnets only to clients that belong to a given class For details on client classes see Section 8 2 17 This is an extension of a previous example from Section 8 2 6 Let s assume that the server is connected to a network segment that uses the 2001 db8 1 64 prefix The Administrator of that network has decided that addresses from range 2001 db8 1 1 to 2001 db8 1 ffff are going to be managed by the Dhcp6 server Only clients belonging to the eRouter1 0 client class are allowed to use that pool Such a configuration can
155. ptions defined in the global scope Stateless and stateful mode can be used together No special configuration directives are required to handle this Simply use the configuration for stateful clients and the stateless clients will get just options they requested This usage of global options allows for an interesting case It is possible to run a server that provides just options and no addresses or prefixes If the options have the same value in each subnet the configuration can define required options in the global scope and skip subnet definitions altogether Here s a simple example of such a configuration HDS xf interfaces config interfaces ethX option data name dns servers data 2001 db8 1 2001 db8 2 lease database type memfile This very simple configuration will provide DNS server information to all clients in the network regardless of their location Note the specification of the memfile lease database this is required since as of version 0 9 1 Kea requires a lease database to be specified even if it is not used 8 6 Using specific relay agent for a subnet The relay has to have an interface connected to the link on which the clients are being configured Typically the relay has a global IPv6 address configured on the interface that belongs to the subnet from which the server will assign addresses In the typical case the server is able to use the IPv6 address inserted by
156. quest and compare that against the name of each reverse DDNS Domain Again the domain whose name matches the longest portion of the FQDN 1s considered the best match For instance 1f the lease address is 172 16 1 40 and there are two reverse domains in the catalog 1 16 172 in addr arpa and 16 172 in addr arpa the former is the best match As with forward matching it is possible to not find a suitable match Given the same two domains there would be no match for the lease address 192 168 1 50 and the request would be rejected Finally if there are no reverse DDNS Domains defined D2 will simply disregard the reverse update portion of requests 9 1 Starting and Stopping the DHCP DDNS Server kea dhcp ddns is the Kea DHCP DDNS server and due to the nature of DDNS it is run alongside either the DHCPv4 or DHCPv6 components or both Like other parts of Kea it is a separate binary that can be run on its own or through keactrl see Chapter 6 In normal operation controlling kea dhcp ddns with keactrl is recommended However it is also possible to run the DHCP DDNS server directly It accepts the following command line switches c file specifies the configuration file This is the only mandatory switch d specifies whether the server logging should be switched to debug verbose mode In verbose mode the logging severity and debuglevel specified in the configuration file are ignored and debug severity and the maximum debuglevel 99
157. r Reference Manual 65 113 The false value of the array parameter determines that the option does NOT comprise an array of uint32 values but rather a single value Two other parameters have been left blank record types and encapsulate The former specifies the comma separated list of option data fields if the option comprises a record of data fields The record fields value should be non empty if the type is set to record Otherwise it must be left blank The latter parameter specifies the name of the option space being encapsulated by the particular option If the particular option does not encapsulate any option space it should be left blank Note that the above set of comments define the format of the new option and do not set its values Once the new option format is defined its value is set in the same way as for a standard option For example the following commands set a global value that applies to all subnets Man A if opr iion darane name foo code 100 space dhcp6 csv format true data 12345 New options can take more complex forms than simple use of primitives uint8 string ipv6 address etc it is possible to define an option comprising a number of existing primitives Assume we want to define a new option that will consist of an IPv6 address followed by an unsigned 16 bit integer followed by a boolean value followed by a text string Such an option could be defined in the following way
158. r a standard option is not required because it is created by default if the standard option is meant to convey any sub options see Section 7 2 9 Assume that we want to have a DHCPv4 option called container with code 222 that conveys two sub options with codes 1 and 2 First we need to define the new sub options Dhcp4 option def name suboptl code 1 space isc type ipv4 address record types array false encapsulate name subopt2 code 2 space isc type string record types array false encapsulate Note that we have defined the options to belong to a new option space in this case isc The next step is to define a regular DHCPv4 option with our desired code and specify that it should include options from the new option space Dhcp4 option def ER name container code 222 space dhcp4 type empty array false record types encapsulate isc The name of the option space in which the sub options are defined is set in the encapsulate field The type field is set to empty to indicate that this option does not carry any data other than sub options Finally we can set values for the new options Dhcp4 operen Catan all name suboptl code 1 space isc data 192 0 2 3 Kea Administrator Reference Manual 37 113 name subopt2 code 2
159. r configuration doesn t match any configured subnet the message is discarded Assuming that the server s interface is configured with the IPv4 address 192 0 2 3 the server will only process messages received through this interface from a directly connected client if there is a subnet configured to which this IPv4 address belongs e g 192 0 2 0 24 The server will use this subnet to assign IPv4 address for the client The rule above does not apply when the client unicasts its message 1 e is trying to renew its lease Such a message is accepted through any interface The renewing client sets ciaddr to the currently used IPv4 address The server uses this address to select the subnet for the client in particular to extend the lease using this address If the message is relayed it is accepted through any interface The giaddr set by the relay agent is used to select the subnet for the client It is also possible to specify a relay IPv4 address for a given subnet It can be used to match incoming packets into a subnet in uncommon configurations e g shared subnets See Section 7 5 1 for details Note The subnet selection mechanism described in this section is based on the assumption that client classification is not used The classification mechanism alters the way in which a subnet is selected for the client depending on the classes to which the client belongs 7 5 1 Using a Specific Relay Agent for a Subnet The relay has to have an
160. r will refuse such a configuration To specify interface id with value vlan123 the following commands can be used DECO subneto Uguonst se 20 sclor lose paisa Weools s Moog 200Ls clos aloevere a spa Ie interface id vlan123 8 2 16 Relay Supplied Options RFC 6422 defines a mechanism called Relay Supplied DHCP Options In certain cases relay agents are the only entities that may have specific information They can insert options when relaying messages from the client to the server The server will then do certain checks and copy those options to the response that will be sent to the client Kea Administrator Reference Manual 71 113 There are certain conditions that must be met for the option to be included First the server must not provide the option by itself In other words 1f both relay and server provide an option the server always takes precedence Second the option must be RSOO enabled IANA mantains a list of RSOO enabled options here However there may be cases when system administrators want to echo other options Kea can be instructed to treat other options as RSOO enabled For example to mark options 110 120 and 130 as RSOO enabled the following syntax should be used Tipe i relay supplied options 110 120 130 As of March 2015 only option 65 is RSOO enabled by IANA This option will always be treated as such and there s no need to explicitly mark it Also when enabling
161. raries Such loggers should have unique names different from the logger names used by Kea In this way the messages emitted from the hooks library can be distingued from messages issued by the core Kea code Unique names also allow the loggers to be configured independently of loggers used by Kea Whenever it makes sense a hook library can use multiple loggers to log messages pertaining to different logical parts of the library In the Logging structure of a configuration file you can specify the configuration for zero or more loggers including loggers used by the proprietary hooks libraries If there are no loggers specified the code will use default values which cause Kea to log messages on at least INFO severity to standard output The three most important elements of a logger configuration are the name the component that is generating the messages the severity what to log and the output_options where to log 15 1 1 1 name string Each logger in the system has a name the name being that of the component binary file using it to log messages For instance if you want to configure logging for the DHCPv4 server you add an entry for a logger named kea dhcp4 This configuration will then be used by the loggers in the DHCPv4 server and all the libraries used by it unless a library defines its own logger and there is specific logger configuration that applies to that logger Kea Administrator Reference Manual 105 113
162. rate DDNS Requests 41 7 2 14 3 kea dhcp4 name generation for DDNS update requests on oo a a 42 7 219 Next Serv r si ddi lt eese d e e e Pe A ee A id A OS 43 7 2 16 Echoing Client ID RFC 68D 43 7 2 17 Using Client Identifier and Hardware Address 2 2 2 ee 44 7 3 Hostreservation in DACPV4 ans e o ee OR RE A EA ORR EER BE EE AE EAH SE eS oS 45 230 Address reservation types 044 44 4 4 e aa k Se See ee ES Eee RSS a eS 46 7 3 2 Conflicts in DHCPv4 reservations ee 46 7 3 3 Reserving ahostname 2 0 Re ar ee ee ee 47 734 Reserving specific options lt 6 s eae 6 eta Se a Seals YESS Bees E s 48 7 3 5 Fine Tuning IPv4 Host Reservation 2 2 2 0 00000 ee ee 48 74 Server Identifier DOCPYA 22 325 h 228 84 940 2H iS A A Oe ede SES 49 7 5 How the DHCPv4 Server Selects a Subnet for the Client o e 49 7 5 1 Using a Specific Relay Agent for a Subnet e 49 7 5 2 Segregating IPv4 Clients in a Cable Network o e 50 7 6 Statistics in DHCPV4 server soacra os ai A Ae 51 7 7 Management API for the DHCPv4 server ee 51 7 8 Supported DHCP Standards 0 0 0 0 00000002 ee 31 79 DHCPv4 Server Limitations 2 0 0 0000 2 53 8 The DHCPv6 Server 54 8 1 Starting and Stopping the DHCPv6 Server 2 ee 54 8 2 DHCPv6 Server Configuration 55 S21 InthoOduchOniins se 4c tik he eee Ge dite Beg rede he a eee ERS he
163. rebind procedures Note that renew timer and rebind timer are optional If they are not specified the client will select values for T1 and T2 timers according to the RFC 2131 The interfaces config map specifies the server configuration concerning the network interfaces on which the server should listen to the DHCP messages The interfaces parameter specifies a list of network interfaces on which the server should listen Lists are opened and closed with square brackets with elements separated by commas Had we wanted to listen on two interfaces the interfaces config would look like this interfaces config interfaces eth0 eth1 The next couple of lines define the lease database the place where the server stores its lease information This particular example tells the server to use memfile which is the simplest and fastest database backend It uses an in memory database and stores leases on disk in a CSV file This is a very simple configuration Usually lease database configuration is more extensive and contains additional parameters Note that lease database is an object and opens up a new scope using an opening brace Its parameters just one in this example type follow Had there been more than one they would be separated by commas This scope is closed with a closing brace As more parameters follow a trailing comma is present Finally we need to define a list of IPv4 subnets This is the most important DHCP v4
164. receive them Non zero value indicates an error One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPOFFER messages towards the server rather back to the clients Number of DHCPREQUEST packets received This statistic is expected to grow Its increase means that clients pkt4 request received integer that just booted received server s response DHCPOFFER accepted it and now requesting an address DHCPREQUEST Number of DHCPACK packets received This statistic is expected to remain zero at all times as DHCPACK packets are sent by the server and the server is never expected pkt4 ack received integer to receive them Non zero value indicates an error One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPACK messages towards the server rather back to the clients Number of DHCPNAK packets received This statistic is expected to remain zero at all times as DHCPNAK packets are sent by the server and the server is never expected pkt4 nak received integer to receive them Non zero value indicates an error One likely cause would be a misbehaving relay agent that incorrectly forwards DHCPNAK messages towards the server rather back to the clients Number of DHCPRELEASE packets received This statistic is expected to pkt4 release received integer grow Its increase means that clients that had an address are shutting down or stop using their addresses Number of DHCPDECLINE pack
165. rfaces config areas 1 WEN leo The asterisk plays the role of a wildcard and means listen on all interfaces However it is usually a good idea to explicitly specify interface names Maat interfaces config Iiacerracess Exa Weyer It is possible to use wildcard interface name asterisk concurrently with explicit interface names Dhcp4 interfaces config Inlineeiataces se EU ETA WEN 1 It is anticipated that this form of usage will only be used when it is desired to temporarily override a list of interface names and listen on all interfaces Some deployments of the DHCP servers require that the servers listen on the interfaces with multiple IPv4 addresses configured In these situations the address to use can be selected by appending an IPv4 address to the interface name in the following manner Doa 3 interfaces config interfaces eth1 10 0 0 1 eth3 192 0 2 3 If it is desired that the server listens on multiple IPv4 addresses assigned to the same interface multiple addresses can be specified for this interface as in the example below Mao af interfaces config interfaces eth1 10 0 0 1 eth1 10 0 0 2 Alternatively if the server should listen on all addresses for the particular interface an interface name without any address should be specified Kea supports responding to directly connected clients which don t have an address configured on the
166. ripts mysql dhcpdb_create mysql pat h to kea is the location where you installed Kea Kea Administrator Reference Manual 12 113 5 Exit MySQL mysql gt quit Bye If you elected not to create the tables in step 4 you can do so now by running the kea admin tool kea admin lease init mysql u database user p database password n database name Do not do this if you did create the tables in step 4 kea admin implements rudimentary checks it will refuse to initialize a database that contains any existing tables If you want to start from scratch you must remove all data manually This process is a manual operation on purpose to avoid possibly irretrievable mistakes by kea admin 4 3 2 2 Upgrading a MySQL Database from an Earlier Version of Kea Sometimes a new Kea version may use newer database schema so there will be a need to upgrade the existing database This can be done using the kea admin lease upgrade command To check the current version of the database use the following command kea admin lease version mysql u database user p database password n database name See Section 4 1 for a discussion about versioning If the version does not match the minimum required for the new version of Kea as described in the release notes the database needs to be upgraded Before upgrading please make sure that the database is backed up The upgrade process does not discard any data but depending on the nature of the
167. s V2 0 2 0 24 Tools sg Woool s 192 0 2 1 I2 02 200 I ho Emasesa V2 Os 0 24 Mooollis s 1 oools YS O 3 100 192 0 3 200 I Va WES WMA 0 A 0 2 Toooles g oool s 192 0 4 1 192 0 4 254 1 When configuring a DHCPv4 server using prefix length notation please pay attention to the boundary values When specifying that the server can use a given pool it will also be able to allocate the first typically network address and the last typically broadcast address address from that pool In the aforementioned example of pool 192 0 3 0 24 both 192 0 3 0 and 192 0 3 255 addresses may be assigned as well This may be invalid in some network configurations If you want to avoid this please use the min max notation 7 2 7 Standard DHCPv4 options One of the major features of the DHCPv4 server is to provide configuration options to clients Most of the options are sent by the server only if the client explicitly requests them using the Parameter Request List option Those that do not require being requested using the Parameter Request List option are commonly used options e g Domain Server and options which require special behavior e g Client FQDN is returned to the client if the client has included this option in its message to the server The Table 7 1 comprises the list of the standard DHCP v4 options whose values can be configured using the configuration struc tures described in this
168. s are enabled and which are disabled The default configuration file is kea install dir etc kea keactrl conf but this can be overridden on a per command basis using the e switch The contents of keactrl conf are Tois ts El Gomi rU arion all for Ieee Seriar Marey Comuizals the startup shutdown reconfiguration and gathering the status of the Kea servers prefix holds the location where the Kea is installed prefix usr local Location of Kea configuration file kea_config_file prefix etc kea kea conf Kea Administrator Reference Manual 18 113 Location of Kea binaries xec_prefix prefix dhcp4_srv exec_prefix sbin kea kea dhcp4 dhcp6_srv exec_prefix sbin kea kea dhcp6 dhcp_ddns_srv exec_prefix sbin kea kea dhcp ddns Start DHCPv4 server dhcp4 yes Start DHCPv6 server dhcp6 yes Start DACP DDN gt S server dhcp_ddns yes Be verbose kea_verbose no The dhcp4 dhcp6 and dhcp_ddns parameters set to yes configure keactrl to manage start reconfigure all servers i e kea dhcp4 kea dhcp6 and kea dhcp ddns When any of these parameters is set to no the keactrl will ignore the corresponding server when starting or reconfiguring Kea By default Kea servers managed by keactrl are located in kea install dir sbin This should work for most instal lations If the default location needs to be altered for any reason the paths specified with the dhcp4_srv dhcp6_srv and
169. s conflict with standard DHCPv6 options so a separate option space must be defined Note that it is not required to create a new option space when defining sub options for a standard option because it is created by default if the standard option is meant to convey any sub options see Section 8 2 10 Assume that we want to have a DHCPv6 option called container with code 102 that conveys two sub options with codes 1 and 2 First we need to define the new sub options Dees if Hoje skon Claiewg name suboptl code 1 space isc type ipv6 address record types array false encapsulate o name subopt2 code 2 space isc type string record types array false encapsulate Note that we have defined the options to belong to a new option space in this case isc The next step is to define a regular DHCP v6 option and specify that it should include options from the isc option space Mica i Ueyieshoin CleieW S 7 name container Kea Administrator Reference Manual 68 113 code 102 space dhcp6 type empty array false record types encapsulate isc The name of the option space in which the sub options are defined is set in the encapsulate field The type field is set to empty which limits this option to only carrying data in sub options Finally we can set values for the new options TDS Gs A Opeo
170. s information introduced in Section 8 6 with client classification explained in Section 8 2 18 One specific example is a cable network where typically modems get addresses from a different subnet than all devices connected behind them Let s assume that there is one CMTS Cable Modem Termination System with one CM MAC a physical link that modems are connected to We want the modems to get addresses from the 3000 64 subnet while everything connected behind modems should get addresses from another subnet 2001 db8 1 64 The CMTS that acts as a relay an uses address 3000 1 The following configuration can serve that configuration Mao if subaebe o Subner US 000 ay oA E O OS toi 3000222 SOQ0 gt Tirs y l client class VENDOR_CLASS_docsis3 0 relay ip address 3000 1 Pr Subasta O 01 sc 00 Moxools 3 Mooeil 3 Y200 cos sil 3s 1 2001 clog 12 g Ee Ie relay ip address 3000 1 Kea Administrator Reference Manual 82 113 8 8 MAC Hardware addresses in DHCPv6 MAC hardware addesses are available in DHCPv4 messages from the clients and administrators frequently use that information to perform certain tasks like per host configuration address reserveration for specific MAC addresses and other Unfortunately DHCPv6 protocol does not provide any completely reliable way to retrieve that information To mitigate that issue a number of mechanisms have been implemented in Kea
171. s prefix reservation types In a typical scenario there s an IPv6 subnet defined with a certain part of it dedicated for dynamic address allocation by the DHCPv6 server There may be an additional address space defined for prefix delegation Those dynamic parts are referred to as dynamic pools address and prefix pools or simply pools In principle the host reservation can reserve any address or prefix that belongs to the subnet The reservations that specify an address that belongs to configured pools are called in pool reservations In contrast those that do not belong to dynamic pools are called out of pool reservations There is no formal difference in the reservation syntax As of 0 9 1 both reservation types are handled uniformly However upcoming releases may offer improved performance if there are only out of pool reservations as the server will be able to skip reservation checks when dealing with existing leases Therefore system administrators are encouraged to use out of pool reservations if possible 8 3 2 Conflicts in DHCPv6 reservations As reservations and lease information are stored in different places conflicts may arrise Consider the following series of events The server has configured the dynamic pool of addresses from the range of 2001 db8 10 to 2001 db8 20 Host A requests an address and gets 2001 db8 10 Now the system administrator decides to reserve an address for host B He decides to reserve 2001 db8 10 for that purpo
172. s the logger used DHCPv6 server deamon to log basic operations kea dhcp6 alloc engine this is the logger used by the lease allocation engine which is responsible for managing leases in the lease database i e create modify and remove DHCPV6 leases as a result of processing messages from the clients kea dhcp6 dhepsrv this is a base logger for the libdhcpsrv library kea dhcp6 hooks this logger is used to log messages related to management of hooks libraries e g registration and deregis tration of the libraries and to the initialization of the callouts execution for various hook points within the DHCPv6 server kea dhcp6 hosts this logger is used within the libdhcpsrv and it logs messages related to the management of the DHCPv6 host reservations i e retrieval of the resevations and adding new reservations kea dhcp6 leases this logger is used by the DHCPv6 server to log messages related to the lease allocation The messages include detailed information about the allocated or offered leases errors during the lease allocation etc kea dhcp6 options this logger is used by the DHCPv6 server to log messages related to processing of the options in the DHCPv6 messages i e parsing options encoding options into on wire format and packet classification using options contained in the received packets kea dhcp6 packets this logger is mostly used to log messages related to transmission of the DHCPv6 packets i e packet reception and
173. s the server to use raw sockets instead If the dhcp socket type value is not specified the default value raw is used Using UDP sockets automatically disables the reception of brodcast packets from directly connected clients This effectively means that the UDP sockets can be used for relayed traffic only When using the raw sockets both the traffic from the directly connected clients and the relayed traffic will be handled Caution should be taken when configuring the server to open multiple raw sockets on the interface with several IPv4 addresses assigned If the directly connected client sends the message to the brodcast address all sockets on this link will receive this message and multiple responses will be sent to the client Hence the configuration with multiple IPv4 addresses assigned to the interface should not be used when the directly connected clients are operating on that link To use a single address on such interface the interface name address notation should be used Note Specifying the value raw as the socket type doesn t guarantee that the raw sockets will be used The use of raw sockets to handle the traffic from the directly connected clients is currently supported on Linux and BSD systems only If the raw sockets are not supported on the particular OS the server will issue a warning and fall back to use the IP UDP sockets 7 2 4 Issues with unicast responses to DHCPINFORM The use of UDP sockets has certain benefits
174. s true false trailer encapsulation 34 boolean false false arp cache timeout 35 uint32 false false EN 36 boolean false false encapsulation default tcp ttl 37 uint8 false false tcp keepalive interval 38 uint32 false false IPEPE PANNE 39 boolean false false garbage Table 7 1 List of standard DHCPv4 options Kea Administrator Reference Manual 33 113 Returned if not Name Code Type Array requested nis domain 40 string false false nis servers 41 1pv4 address true false ntp servers 42 1pv4 address true false as AE 43 empty false false options netbios name servers 44 ipv4 address true false netbios dd server 45 ipv4 address true false netbios node type 46 uint8 false false netbios scope 47 string false false font servers 48 ipv4 address true false x display manager 49 ipv4 address true false dhcp option overload 52 uint8 false false dhcp message 56 string false false e la uint16 false false size Nias g 60 binary false false nwip domain name 62 string false false nwip suboptions 63 binary false false tftp server name 66 string false false boot file name 67 string false false user class 77 binary false false subnet selection 118 ipv4 address false false domain search 119 binary false false vivco suboptions 124 binary false false vivso suboptions 125 binary false false Table 7 2 List of standard DHCPv4 options continued
175. sconfigured device in a network may cause clients to report duplicate addresses so the server will report increasing values of pkt4 decline received Once the problem is found and the device is removed the system administrator may want to remove the pkt4 decline received statistic so it won t be reported anymore If a duplicate address is detected ever again the server will add this statistic back 12 3 Commands for Manipulating Statistics There are several commands defined that can be used for accessing get resetting to zero or neutral value reset or even removing a statistic completely remove The difference between reset and remove is somewhat subtle The reset command sets the value of the statistic to zero or neutral value After this operation the statistic will have a value of 0 integer 0 0 float OhOm0sOus duration or string When asked for a statistic with the values mentioned will be returned Remove removes a statistic completely so the statistic will not be reported anymore Please note that the server code may add it back if there s a reason to record it 12 3 1 statistic get command statistic get command retrieves a single statistic It takes a single string parameter called name that specifies the statistic name An example command may look like this Mecenas Wer elias a oe arguments name pkt4 received The server will respond with details of the requested statistic with result set to O
176. se In general reserving an address that is currently assigned to someone else is not recommended but there are valid use cases where such an operation is warranted The server now has a conflict to resolve Let s analyze the situation here If host B boots up and request an address the server is not able to assign the reserved address 2001 db8 10 A naive approach would to be immediately remove the lease for host A and create a new one for host B That would not solve the problem though because as soon as host B get the address it will detect that the address is already in use by someone else host A and would send Decline Therefore in this situation the server has to temporarily assign a different address from the dynamic pool not matching what has been reserved to host B When the host A renews its address the server will discover that the address being renewed is now reserved for someone else host B Therefore the server will remove the lease for 2001 db8 10 and select a new address and will create a new lease for it It will send two addresses in its response the old address with lifetimes set to 0 to explicitly indicate that it is no longer valid and a new address with non zero lifetimes When the host B renews its temporarily assigned address the server will detect that the existing lease does not match reservation so it will release the current address host B has and will create a new lease matching Kea Administrator Reference
177. se or creates a new lease for the client the new lease information must be recorded in the lease file For performance reasons the server does not supersede the existing client s lease as it would require the lookup of the specific lease entry but simply appends the new lease information at the end of the lease file The previous lease entries for the client are not removed When the server loads leases from the lease file e g at the server startup it assumes that the latest lease entry for the client is the valid one The previous entries are discarded This means that the server can re construct the accurate information about the leases even though there may be many lease entries for each client However storing many entries for each client results in bloated lease file and impairs the performance of the server s startup and reconfiguration as it needs to process larger number of lease entries The lease file cleanup removes all previous entries for each client and leaves only the latest ones The interval at which the cleanup is performed is configurable and it should be selected according to the frequency of lease renewals initiated by the clients The more frequent renewals are the lesser value of the Ifc interval should be Note however that the LFC takes time Kea Administrator Reference Manual 25 113 and thus it is possible although unlikely that new cleanup is started while the previous cleanup instance is still running if th
178. section This table excludes the options which require special processing and thus cannot be configured with some fixed values The last column of this table specifies which options can be sent by the server even when they are not requested in the Parameter Request list option and which are sent only when explicitly requested These options are marked with the values true and false respectively The following example shows how to configure the addresses of DNS servers which is one of the most frequently used options Options specified in this way are considered global and apply to all configured subnets Dhcp4 Hopelton daran a name domain name servers code 6 space dhcp4 Kea Administrator Reference Manual 30 113 csv format true data 192 0 2 1 192 0 2 2 The name parameter specifies the option name For a list of currently supported names see Table 7 1 below The code parameter specifies the option code which must match one of the values from that list The next line specifies the option space which must always be set to dhcp4 as these are standard DHCPv4 options For other option spaces including custom option spaces see Section 7 2 10 The next line specifies the format in which the data will be entered use of CSV comma separated values is recommended The sixth line gives the actual value to be sent to clients Data is specified as normal text with values separated by commas i
179. server checks if the address belongs to a defined subnet and if it does that subnet is selected for the client s request The second mechanism is based on interface id options While forwarding a client s message relays may insert an interface id option into the message that identifies the interface on the relay that received the message Some relays allow configuration of that parameter but it is sometimes hardcoded and may range from the very simple e g vlan100 to the very cryptic one example seen on real hardware was ISAM144 290lipv6lnt vp 1 110 The server can use this information to select the appropriate subnet The information is also returned to the relay which then knows the interface to use to transmit the response to the client In order for this to work successfully the relay interface IDs must be unique within the network and the server configuration must match those values When configuring the DHCPV6 server it should be noted that two similarly named parameters can be configured for a subnet e interface defines which local network interface can be used to access a given subnet e interface id specifies the content of the interface id option used by relays to identify the interface on the relay to which the response packet is sent The two are mutually exclusive a subnet cannot be both reachable locally direct traffic and via relays remote traffic Speci fying both is a configuration error and the DHCPv6 serve
180. sic JSON is defined in RFC 4627 Kea components use a slightly modified JSON in that they allow shell style comments in the file lines with the hash character in the first column are comment lines and are ignored The configuration file consists of a single object often colloquially called a map started with a curly bracket It comprises the Dhcp4 Dhcp6 DhcpDdns and or Logging objects It is possible to define additional elements but they will be ignored For example it is possible to define Dhcp4 Dhcp6 and Logging elements in a single configuration file that can be used to start both the DHCPv4 and DHCPv6 components When starting the DHCPv4 component will use Dhcp4 object to configure itself and the Logging object to configure logging parameters it will ignore the Dhcp6 object For example a very simple configuration for both DHCPv4 and DHCPv6 could look like this The whole configuration starts here DHCPv4 specific configuration starts here Mpineroa g i Wintertaces config acertados e eco 1 dhcp socket type raw valia Alte timeni 00 05 renew timer 1000 rebind timer 2000 subnet4t 4 Masas Ys 4 Wooouli s 192 0 2 1 192 0 2 200 17 ena MIE 2 OA Am lg Kea Administrator Reference Manual 16 113 DHCPv4 specific configuration ends here DHCPv6 specific configuration starts here Monago interfaces config interfaces Mejia a preferr
181. socket and will listen for any incoming connections process connecting to this socket is expected to send JSON commands structured as follows commen Too arguments paraml valuel oem s VayeulneZ command is the name of command to execute and is mandatory arguments is a map of parameters required to carry out the given command The exact content and format is command specific The server will process the incoming command and then send a response of the form result 011 text textual description argument sue argument1 valuel argument2 value2 Kea Administrator Reference Manual 102 113 result indicates the outcome of the command A value of O means success while any non zero value designates an error Currently 1 is used as a generic error but additional error codes may be added in the future text field typically appears when result is non zero and contains a description of the error encountered but it may also appear for successful results That s command specific arguments is a map of additional data values returned by the server specific to the command issued The map is always present even if it contains no data values 13 2 Using control channel ISC does not provide a client for using control channel The primary reason for that is the expectation is that the entity using con trol channel is typically an IPAM or similar network management monitoring software which may h
182. specifies which hashing algorithm should be used with this key This value must specify the same algorithm used for the key on the DNS server s The supported algorithms are listed below Kea Administrator Reference Manual 89 113 HMAC MD5 HMAC SHA1 HMAC SHA224 HMAC SHA256 HMAC SHA384 HMAC SHA512 This value is not case sensitive digest_bits is used to specify the minimum truncated length in bits The default value O means truncation is forbidden not 0 values must be an integral number of octets be greater than 80 and the half of the full length Note in BIND9 this parameter is appended after a dash to the algorithm name secret is used to specify the shared secret key code for this key This value is case sensitive and must exactly match the value specified on the DNS server s It is a base64 encoded text value As an example suppose that a domain D2 will be updating is maintained by a BIND9 DNS server which requires dynamic updates to be secured with TSIG Suppose further that the entry for the TSIG key in BIND9 s named conf file looks like this key key four example com algorithm hmac sha224 secret bZEG70w80gAUPfLWV3aAUQ y By default the TSIG Key list is empty MiDiacroDyolbossS 4h tsig keys We must extend the list with a new key gases Besa iS ll 1 name key four example com algorithm HMAC SHA224 secret bZEG70w80gAUPfLWV3aAUQ r
183. st Reservation Note reservation mode in the DHCPV6 server is implemented in Kea 0 9 1 but has not been tested and is considered experimental Host reservation capability introduces additional restrictions for the allocation engine during lease selection and renewal In particular three major checks are necessary First when selecting a new lease it is not sufficient for a candidate lease to be not used by another DHCP client It also must not be reserved for another client Second when renewing a lease additional check must be performed whether the address being renewed is not reserved for another client Finally when a host renews an address or a prefix the server has to check whether there s a reservation for this host so the existing dynamically allocated address should be revoked and the reserved one be used instead Some of those checks may be unnecessary in certain deployments Not performing them may improve performance The Kea server provides the reservation mode configuration parameter to select the types of reservations allowed for the particular subnet Each reservation type has different constraints for the checks to be performed by the server when allocating or renewing a lease for the client Allowed values are e all enables all host reservation types This is the default value This setting is the safest and the most flexible It allows in pool and out of pool reservations As all checks are conducted it is also the s
184. st be well formed JSON That means that parameters for any given scope must be separated by a comma and there must not be a comma after the last parameter When reordering a configuration file keep in mind that moving a parameter to or from the last position in a given scope may require moving the comma as well The second caveat is that it is uncommon although legal JSON to repeat the same parameter multiple times If that happens the last occurrence of a given parameter in a given scope is used while all previous instances are ignored This is unlikely to cause any confusion as there are no real life reasons to keep multiple copies of the same parameter in your configuration file Moving onto the DHCPv6 configuration elements the very first few elements define some global parameters valid lifetime defines for how long the addresses leases given out by the server are valid If nothing changes a client that got an address is allowed to use it for 4000 seconds Note that integer numbers are specified as is without any quotes around them The address will become deprecated in 3000 seconds clients are allowed to keep old connections but can t use this address for creating new connections renew timer and rebind timer are values that define T1 and T2 timers that govern when the client will begin the renewal and rebind procedures The interfaces config map specifies the server configuration concerning the network interfaces on which the serv
185. sts allowed to queue waiting to be sent to D2 This value guards against requests accumulating uncontrollably if they are being generated faster than they can be delivered If the number of requests queued for transmission reaches this value DDNS updating will be turned off until the queue backlog has been sufficiently reduced The intent is to allow kea dhcp6 to continue lease operations The default value is 1024 ncr format Socket protocol use when sending requests to D2 Currently only UDP is supported TCP may be available in an upcoming release ncr protocol Packet format to use when sending requests to D2 Currently only JSON format is supported Other formats may be available in future releases By default kea dhcp ddns is assumed to running on the same machine as kea dhcp6 and all of the default values mentioned above should be sufficient If however D2 has been configured to listen on a different address or port these values must altered accordingly For example if D2 has been configured to listen on 2001 db8 5 port 900 the following commands would be required UIDoeiots 4 f Uclavero ckoiosy server ip 2001 db8 5 server port 900 8 2 19 2 When does kea dhcp6 generate DDNS request kea dhcp6 follows the behavior prescribed for DHCP servers in RFC 4704 It is important to keep in mind that kea dhcp6 provides the initial decision making of when and what to update and forwards that information to D2 in the for
186. t require any framework and thus is considered more lightweight It will allow dynamic on line reconfiguration but will lack remote capabilities i e no RESTful APD 3 6 DHCP Database Installation and Configuration Kea stores its leases in a lease database The software has been written in a way that makes it possible to choose which database product should be used to store the lease information At present Kea supports three database backends MySQL PostgreSQL and Memfile To limit external dependencies both MySQL and PostgreSQL support are disabled by default and only Memfile is available Support for the optional external database backend must be explicitly included when Kea is built This section covers the building of Kea with MySQL and or PostgreSQL and the creation of the lease database 3 6 1 Building with MySQL Support Install MySQL according to the instructions for your system The client development libraries must be installed Build and install Kea as described in Chapter 3 with the following modification To enable the MySQL database code at the configure step see Section 3 4 3 do configure other options with dhcp mysql Or specify the location of the MySQL configuration program mysql_config if MySQL was not installed in the default location configure other options with dhcp mysql path to mysql_config See Section 4 3 2 1 for details regarding MySQL database configuration Kea Administrator Reference
187. t in the global scope or for a given subnet only If both are defined the subnet value takes precedence The value in subnet can be set to 0 0 0 0 which means that next server should not be sent It may also be set to an empty string which means the same as if it was not defined at all i e use the global value DAA 3 f next server 192 0 2 123 subnet4 next server 192 0 2 234 7 2 16 Echoing Client ID RFC 6842 The original DHCP V4 specification RFC 2131 states that the DHCPv4 server must not send back client id options when re sponding to clients However in some cases that confused clients that did not have MAC address or client id see RFC 6842 for details That behavior has changed with the publication of RFC 6842 which updated RFC 2131 That update now states that the server must send client id if the client sent it That is the default behaviour that Kea offers However in some cases older devices that do not support RFC 6842 may refuse to accept responses that include the client id option To enable backward compatibility an optional configuration parameter has been introduced To configure it use the following configuration statement Kea Administrator Reference Manual 44 113 Dhcp4 echo client id false 7 2 17 Using Client Identifier and Hardware Address DHCP server must be able to identify the client distinguish it from other clients from which it receives the message There are many re
188. t take any arguments An example command may look like this command shutdown arguments The server will respond with a confirmation that the shutdown procedure has been initiated Kea Administrator Reference Manual 103 113 Chapter 14 libdhcp library libdhcp is a common library written in C that handles many DHCP related tasks including e DHCPv4 and DHCPv6 packets parsing manipulation and assembly e Option parsing manipulation and assembly e Network interface detection e Socket operations such as creation data transmission and reception and socket closing While this library is currently used by Kea it is designed to be a portable universal library useful for any kind of DHCP related software 14 1 Interface detection and Socket handling Both the DHCPv4 and DHCPv6 components share network interface detection routines Interface detection is currently supported on Linux all BSD family FreeBSD NetBSD OpenBSD Mac OS X and Solaris 11 systems DHCPv4 requires special raw socket processing to send and receive packets from hosts that do not have IPv4 address assigned yet Support for this operation is implemented on Linux FreeBSD NetBSD and OpenBSD It is likely that DHCPv4 component will not work in certain cases on other systems Kea Administrator Reference Manual 104 113 Chapter 15 Logging 15 1 Logging Configuration During its operation Kea may produce many messages They di
189. t the FODN N and S flags specified by the client as shown in the following table Client Flags N S Client Intent Server Response Server Flags N S O Client wants to do forward petaca 0 0 updates server should do 8 1 0 0 reverse only request reverse updates 0 1 Server should do both Server generates request to 0 1 0 forward and reverse updates update both directions Client wants no updates Server does not generate a 1 0 1 0 0 done request Table 8 2 Default FQDN Flag Behavior The first row in the table above represents client delegation Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverse updates By default kea dhcp6 will honor the client s wishes and generate a DDNS request to D2 to update only reverse DNS data The parameter override client update can be used to instruct the server to override client delegation requests When this parameter is true kea dhcp6 will disregard requests for client delegation and generate a DDNS request to update both forward and reverse DNS data In this case the N S O flags in the server s response to the client will be 0 1 1 respectively Note that the flag combination N 1 S 1 is prohibited according to RFC 4702 If such a combination is received from the client the packet will be dropped by kea dhcp6 To override client delegation issue the following commands ADEDE if WY GING aC Clits sl override cl
190. t this value may be overridden at run time by setting the environment variable KEA_PIDFILE_DIR This is intended primarily for testing purposes Kea Administrator Reference Manual 55 113 e conf name The confguration file name used to start the server minus all preceding path and file extension For example given a pathname of usr local etc kea myconf txt the portion used would be myconf If the file already exists and contains the PID of a live process the server will issue a DHCP6_ALREADY_ RUNNING log message and exit It is possible though unlikely that the file is a remnant of a system crash and the process to which the PID belongs is unrelated to Kea In such a case it would be necessary to manually delete the PID file 8 2 DHCPv6 Server Configuration 8 2 1 Introduction This section explains how to configure the DHCPv6 server using the Kea configuration backend Kea configuration using any other backends is outside of scope of this document Before DHCPV6 is started its configuration file has to be created The basic configuration looks as follows DHCPv6 configuration starts on the next line MRS B a First we set up global values renew timer 1000 rebind timer 2000 preferred lifetime 3000 valid lifetime 4000 Next we setup the interfaces to be used by the server interfaces config interfaces eth0 And we specify the type of a lease database lease da
191. tabase type memfile persist true name var kea dhcp6 leases Finally we list the subnets from which we will be leasing addresses subnet6 Varionet g WAO OLS cl is 9 GAN MODOS Mae MANO scans 8 Sil Z0 Pe Cloxss 8 iL Sita e DHCPv6 configuration ends with the next line The following paragraphs provide a brief overview of the parameters in the above example and their format Subsequent sections of this chapter go into much greater detail for these and other parameters The lines starting with a hash are comments and are ignored by the server they do not impact its operation in any way The configuration starts in the first line with the initial opening curly bracket or brace Each configuration consists of one or more objects In this specific example we have only one object called Dhcp6 This is a simplified configuration as usually there Kea Administrator Reference Manual 56 113 will be additional objects like Logging or DhcpDns but we omit them now for clarity The Dhcp6 configuration starts with the Dhcp6 line and ends with the corresponding closing brace in the above example the brace after the last comment Everything defined between those lines is considered to be the Dhcp6 configuration In the general case the order in which those parameters appear does not matter There are two caveats here though The first one is to remember that the configuration file mu
192. ted by the server to the file The appropriate name for the logger could be kea dhcp4 packet capture Note that the hook library implementor only specifies the second part of this name i e packet capture The first part is a root logger name and is prepended by the Kea logging system It is also important to note that since this new logger is a child of a root logger it Kea Administrator Reference Manual 107 113 inherits the configuration from the root logger unless there is a separate configuration entry for the child logger which overrides the default configuration The list of loggers above excludes any loggers implemented in hooks libraries Please consult the documentation of the specific hooks libraries for the names of loggers they define Additional loggers may be defined in the future The easiest way to find out the logger name is to configure all logging to go to a single destination and look for specific logger names See Section 15 2 for details 15 1 1 2 severity string This specifies the category of messages logged Each message is logged with an associated severity which may be one of the following in descending order of severity e FATAL e ERROR e WARN e INFO e DEBUG When the severity of a logger is set to one of these values it will only log messages of that severity and the severities above it The severity may also be set to NONE in which case all messages from that logger are inhibited 15 1 1
193. that attempt to gather that information Each of those mechanisms works in certain cases but may fail in other cases Whether the mechanism works or not in the particular deployment is somewhat dependent on the network topology and the technologies used Kea allows for configuration which of the supported methods should be used and in which order This configuration may be considered a fine tuning of the DHCP deployment In a typical deployment the default value of any is sufficient and there is no need to select specific methods Changing the value of this parameter is the most useful in cases when an administrator wants to disable certain method e g if the administrator trusts the network infrastructure more than the information provided by the clients themselves the administrator may prefer information provided by the relays over that provided by the clients The format of this parameter is as follows Un if mac sources method1 method2 method3 subneto new dy When not specified a special value of any is used which instructs the server to attempt to use all the methods in sequence and use value returned by the first one that succeeds Supported methods are any not an actual method just a keyword that instructs Kea to try all other methods and use the first one that succeeds This is the default operation if no mac sources are defined raw In principle a DHCPV6 server could use raw sockets to receive incomi
194. the relay in the link addr field in RELAY FORW message to select the appropriate subnet However that is not always the case The relay address may not match the subnet in certain deployments This usually means that there is more than one subnet allocated for a given link The two most common examples where this is the case are long lasting network renumbering where both old and new address space is still being used and a cable network In a cable network both cable modems and the devices behind them are physically connected to the same link yet they use distinct addressing In such case the DHCPv6 server needs additional information like the value of interface id option or IPv6 address inserted in the link addr field in RELAY FORW message to properly select an appropriate subnet The following example assumes that there is a subnet 2001 db8 1 64 that is accessible via relay that uses 3000 1 as its IPv6 address The server will be able to select this subnet for any incoming packets that came from a relay that has an address in 2001 db8 1 64 subnet It will also select that subnet for a relay with address 3000 1 Kea Administrator Reference Manual 81 113 DEco cre subrete Uslomac e V200 coes Les Gly Macas Moe VINO close il ss i1i 2001 close ILS siere see e Ip relay ip address 3000 1 8 7 Segregating IPv6 clients in a cable network In certain cases it is useful to mix relay addres
195. tic remove statistic get all statistic reset all and statistic remove all specified in Section 12 3 It also supports list commands and shutdown specified in Section 13 3 1 and Section 13 3 2 respectively 8 11 Supported DHCPv6 Standards The following standards are currently supported e Dynamic Host Configuration Protocol for IPv6 RFC 3315 Supported messages are SOLICIT ADVERTISE REQUEST RELEASE RENEW REBIND INFORMATION REQUEST CONFIRM and REPLY Kea Administrator Reference Manual 84 113 Statistic Data Type Description Number of DHCPv6 packets received This includes all packets valid bogus corrupted rejected etc This statistic is expected to grow rapidly Number of incoming packets that were dropped Exact reason for dropping packets is logged but the most common reasons may be an pkt6 receive drop integer unacceptable or not supported packet type direct responses are forbidden the server id sent by the client does not match the server s server id or the packet is malformed Number of incoming packets that could not be parsed A non zero value of this statistic indicates that the server pkt6 parse failed integer received a malformed or truncated packet This may indicate problems in your network faulty clients faulty relay agents or server code bug Number of SOLICIT packets received This statistic is expected to grow Its increase means that clients that just booted started their configurati
196. to do the forward DNS updates and the server should do the reverse updates By default kea dhcp4 will honor the client s wishes and generate a DDNS request to the DHCP DDNS server to update only reverse DNS data The parameter override client update can be used to instruct the server to override client delegation requests When this parameter is true kea dhcp4 will disregard requests for client delegation and generate a DDNS request to update both forward and reverse DNS data In this case the N S O flags in the server s response to the client will be 0 1 1 respectively Note that the flag combination N 1 S 1 is prohibited according to RFC 4702 If such a combination is received from the client the packet will be dropped by kea dhcp4 To override client delegation set the following values in your configuration file Kea Administrator Reference Manual 42 113 DRG PATE E Wgliaxvejo Cleins te i override client update true The third row in the table above describes the case in which the client requests that no DNS updates be done The parameter override no update can be used to instruct the server to disregard the client s wishes When this parameter is true kea dhcp4 will generate a DDNS update request to kea dhcp ddns even if the client requests that no updates be done The N S O flags in the server s response to the client will be 0 1 1 To override client delegation the following values should be set in your co
197. ts when 1 A new lease is granted in response to a DHCP REQUEST 2 An existing lease is renewed but the FQDN associated with it has changed 3 An existing lease is released in response to a DHCP RELEASE In the second case lease renewal two DDNS requests will be issued one request to remove entries for the previous FQDN and a second request to add entries for the new FQDN In the last case a lease release a single DDNS request to remove its entries will be made The decision making involved when granting a new lease the first case is more involved and is discussed next When a new lease is granted kea dhcp4 will generate a DDNS update request if the DHCP REQUEST contains either the FQDN option code 81 or the Host Name option code 12 If both are present the server will use the FQDN option By default kea dhcp4 will respect the FQDN N and S flags specified by the client as shown in the following table Client Flags N S Client Intent Server Response Server Flags N S O Client wants to do forward ais 0 0 updates server should do 8 1 0 0 reverse only request reverse updates 0 1 Server should do both Server generates request to 0 1 0 forward and reverse updates update both directions Client wants no updates Server does not generate a 1 0 1 0 0 done request Table 7 4 Default FQDN Flag Behavior The first row in the table above represents client delegation Here the DHCP client states that it intends
198. ue of the persist parameter is true which enables writing lease updates to the lease file e name specifies an absolute location of the lease file in which new leases and lease updates will be recorded The default value for this parameter is kea install dir var kea kea leases6 csv e Ifc interval specifies the interval in seconds at which the server Memfile backend will perform a lease file cleanup LFC which removes the redundant historical information from the lease file and effectively reduces the lease file size The cleanup process is described in more detailed fashion further in this section The default value of the Ife interval is O which disables the LFC The example configuration of the Memfile backend is presented below DECO CA lease database type memfile persist true name tmp kea leases6 csv lfc interval 1800 It is important to know how the lease file contents are organized to understand why the periodic lease file cleanup is needed Every time when the server updates a lease or creates a new lease for the client the new lease information must be recorded in the lease file For performance reasons the server does not supersede the existing client s lease as it would require the lookup of the specific lease entry but simply appends the new lease information at the end of the lease file The previous lease entries for the client are not removed When the server loads leases from the lease fi
199. uglevel specified in the configuration file are ignored and debug severity and the maximum debuglevel 99 are assumed The flag is convenient for temporarily switching the server into maximum verbosity e g when debugging p port specifies UDP port the server will listen on This is only useful during testing as the DHCPv4 server listening on ports other than default DHCPv4 ports will not be able to handle regular DHCPv4 queries y prints out Kea version and exits V prints out Kea extended version with additional parameters and exits W prints out Kea configuration report and exits The V command returns the versions of the external libraries dynamically linked The W command describes the environment used to build Kea This command displays a copy of the config report file produced by configure that is embedded in the executable binary The config report may also be accessed more directly The following command may be used to extract this information The binary path may be found in the install directory or in the 1ibs subdirectory in the source treee For example kea src bin dhcp4 1libs kea dhcp4 strings path kea dhcp4 sed n s p When running in a console the server can be shut down by pressing ctrl c It detects the key combination and shuts down gracefully On start up the server will detect available network interfaces and will attempt to open UDP sockets on all interfaces mentioned in the co
200. uired 4 3 2 MySQL The MySQL database must be properly set up if you want Kea to store information in MySQL This section can be safely ignored 1f you chose to store the data in other backends 4 3 2 1 First Time Creation of Kea Database If you are setting the MySQL database for the first time you need to create the database area within MySQL and set up the MySQL user ID under which Kea will access the database This needs to be done manually kea admin is not able to do this for you To create the database 1 Log into MySQL as root mysql u root p Enter password mysql gt 2 Create the MySQL database mysql gt CREATE DATABASE database name database name is the name you have chosen for the database 3 Create the user under which Kea will access the database and give it a password then grant it access to the database tables mysql gt CREATE USER user name localhost IDENTIFIED BY password mysql gt GRANT ALL ON database name TO user name localhost user name and password are the user ID and password you are using to allow Keas access to the MySQL instance All apostrophes in the command lines above are required 4 At this point you may elect to create the database tables Alternatively you can exit MySQL and create the tables using the kea admin tool as explained below To do this mysql gt CONNECT database name mysql gt SOURCE path to kea share kea sc
201. uthenticated access to Kea s database local database nam user nam password host database nam user nam 12700 1 32 password host database nam user nam sg ILZE password These edits are primarily intended as a starting point not a definitive reference on PostgreSQL administration or database security Please consult your PostgreSQL user manual before making these changes as they may expose other databases that you run It may be necessary to restart PostgreSQL in order for these changes to take effect Kea Administrator Reference Manual 14 113 4 3 3 2 Initialize the PostgreSQL Database Using kea admin If you elected not to create the tables manually you can do so now by running the kea admin tool kea admin lease init pgsql u database user p database password n database name Do not do this if you already created the tables in manually kea admin implements rudimentary checks it will refuse to initialize a database that contains any existing tables If you want to start from scratch you must remove all data manually This process is a manual operation on purpose to avoid possibly irretrievable mistakes by kea admin 4 3 3 3 Upgrading a PostgreSQL Database from an Earlier Version of Kea Currently PostgreSQL only supports Kea schema version 1 0 so no upgrades are available As upgrades become available kea admin will support them 4 3 4 Limitations related to the use of the SQL databases The lease expiration time
202. veloped by ISC which is a non profit organization You may consider signing a development contract with us In the past we did implement certain features due to contractual obligations With additional funds we are able to put extra engineering efforts into Kea development We can reshuffle our schedule or add extra hands to the team if needed Please keep in mind that Kea is open source software and its principle goal is to provide a good DHCP solution that can be used by everyone In other words we may refuse a contract that would tie the solution to specific proprietary technology or make it unusable for other users Also we strive to make Kea a reference implementation so if your proposal significantly violates a RFC we may have a problem with that Nevertheless please talk to us and we may be able to find a solution Kea Administrator Reference Manual 112 113 Finally Kea has a public roadmap with releases happening several times each year We tend to not modify plans for the current milestone unless there are very good reasons to do so Therefore Td like a feature X in 6 months is much better received than Pd like a feature X now 16 2 Frequently Asked Questions about DHCPv4 16 2 1 set up a firewall but the Kea server still receives the traffic Why Any DHCPv4 server must be able to receive from and send traffic to hosts that don t have an IPv4 address assigned yet That 1s typically not possible with regular UDP sockets th
203. ver side of the DDNS protocol for this domain Currently the servers are used in a first to last preference In other words when D2 begins to process a request for this domain it will pick the first server in this list and attempt to communicate with it If that attempt fails it will move to next one in the list and so on until the it achieves success or the list is exhausted Kea Administrator Reference Manual 92 113 To create a new reverse DDNS Domain one must add a new domain element and set its parameters For example to support subnet 2001 db8 1 the following configuration could be used UDHECPDAN SAE E reverse_ddns dadas doma ias Il 1 name 1 0 0 0 8 B D 0 1 0 0 2 ip6 arpa key name dns _ servers It is permissible to add a domain without any servers If that domain should be matched to a request however the request will fail In order to make the domain useful though we must add at least one DNS server to it 9 2 4 1 1 Adding Reverse DNS Servers This section describes how to add DNS servers to a Reverse DDNS Domain Repeat them for as many servers as desired for each domain Reverse DNS Server entries represents a actual DNS servers which support the server side of the DDNS protocol Each Reverse DNS Server has the following parameters e hostname The resolvable host name of the DNS server This value is currently ignored e ip_address The IP address at which the server listens for DD
204. when renewing a lease additional check must be performed whether the address being renewed is not reserved for another client Finally when a host renews an address the server has to check whether there s a reservation for this host so the exisiting dynamically allocated address should be revoked and the reserved one be used instead Some of those checks may be unnecessary in certain deployments Not performing them may improve performance The Kea server provides the reservation mode configuration parameter to select the types of reservations allowed for the particular subnet Each reservation type has different constraints for the checks to be performed by the server when allocating or renewing a lease for the client Allowed values are e all enables all host reservation types This is the default value This setting is the safest and the most flexible It allows in pool and out of pool reservations As all checks are conducted it is also the slowest e out of pool allows only out of pool host reservations With this setting in place the server may assume that all host reserva tions are for addresses that do not belong to the dynamic pool Therefore it can skip the reservation checks when dealing with in pool addresses thus improving performance Do not use this mode if any of your reservations use in pool address Caution is advised when using this setting Kea 0 9 2 does not sanity check the reservations against reservation mode Miscon
205. which can be used as an index into the Kea Messages Manual http kea isc org docs kea messages html from which more information can be obtained opening memory file lease database type memfile universe 4 A brief description Within this text information relating to the condition that caused the message to be logged will be included In this example the information is logged that the in memory lease database backend will be used to store DHCP leases 15 3 Logging During Kea Startup The logging configuration is specified in the configuration file However when Kea starts the file is not read until some way into the initialization process Prior to that the logging settings are set to default values although it is possible to modify some aspects of the settings by means of environment variables Note that in the absence of any logging configuration in the configuration file the settings of possibly modified default configuration will persist while the program is running The following environment variables can be used to control the behavio of logging during startup Kea Administrator Reference Manual 110 113 KEA_LOCKFILE_DIR Specifies a directory where the logging system should create its lock file If not specified it is pre fix var run kea where prefix defaults to usr local This variable must not end with a slash There is one special value none which instructs Kea to not create lock file at all This may cause issues
206. wn as NameChangeRequests NCRs based upon DHCP lease change events and then post these to D2 D2 attempts to match each such request to the appropriate DNS server s and carry out the necessary conversation with those servers to update the DNS data In order to match a request to the appropriate DNS servers D2 must have a catalog of servers from which to select In fact D2 has two such catalogs one for forward DNS and one for reverse DNS these catalogs are referred to as DDNS Domain Lists Each list consists of one or more named DDNS Domains Further each DDNS Domain has a list of one or more DNS servers that publish the DNS data for that domain When conducting forward domain matching D2 will compare the FQDN in the request against the name of each forward DDNS Domain The domain whose name matches the longest portion of the FQDN is considered the best match For example if the FQDN is myhost sample example com and there are two forward domains in the catalog sample example com and example com the former is regarded as the best match In some cases it may not be possible to find a suitable match Given the same two forward domains there would be no match for the FQDN bogus net so the request would be rejected Finally if there are no forward DDNS Domains defined D2 will simply disregard the forward update portion of requests When conducting reverse domain matching D2 constructs a reverse FODN from the lease address in the re

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