Lab - Troubleshooting DHCPv4
Contents
1. DHCP debug command to observe the DHCP process on R2 R2 debug ip dhcp server events Di R1 show run interface g0 0 splay the running configuration for the G0 0 interface on R1 to identify possible DHCP issues interface GigabitEthernet0 0 ip address 192 168 0 1 255 255 255 128 duplex auto speed auto Record the issues and any commands that are necessary to correct the configurations errors From the command prompt on PC B type ipconfig renew to receive an address from the DHCP server Record the configured IP address subnet mask and default gateway for PC B Observe the debug messages on R2 router for the renewal process for PC A The DHCP server assigned 192 168 0 10 25 to PC B Mar 5 07 15 09 663 DHCPD Sending notification of DISCOVER Mar 5 07 15 09 663 DHCPD htype 1 chaddr 0050 56be f6db Mar 5 07 15 09 663 DHCPD circuit id 00000000 Mar 5 07 15 09 663 DHCPD Seeing if there is an internally specified pool class Mar 5 07 15 09 663 DHCPD htype 1 chaddr 0050 56be f6db Mar 5 07 15 09 663 DHCPD circuit id 00000000 Mar 5 07 15 09 707 DHCBDE S ndiing ROtMELeation Oe ASSIGNMENT Mar 5 07 15 09 707 DHCPD add ess 192116810010 mask 255 255 2550028 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public Page 7 of 8 Lab Troubleshooting DHCPv4 Mar Mar 5 OF 215209 7074 5 O7315209 707s e Verify network connectivity Can PC B pi2. 3 universal image or comparable Page 2 of 8 Lab Troubleshooting DHCPv4 2 Switches Cisco 2960 with Cisco IOS Release 15 0 2 lanbasek9 image or comparable 2 PCs Windows 7 Vista or XP with terminal emulation program such as Tera Term Console cables to configure the Cisco IOS devices via the console ports Ethernet and serial cables as shown in the topology Part 2 Build the Network and Configure Basic Device Settings In Part 1 you will set up the network topology and configure the routers and switches with basic settings such as passwords and IP addresses You will also configure the IP settings for the PCs in the topology Step 1 Cable the network as shown in the topology Step 2 Initialize and reload the routers and switches Step 3 Configure basic settings for each router a Oo a9 5 gt Disable DNS lookup Configure device name as shown in the topology Assign class as the privileged EXEC password Assign cisco as the console and vty passwords Configure logging synchronous to prevent console messages from interrupting command entry Configure the IP addresses for all the router interfaces Set clock rate to 128000 for all DCE router interfaces Configure EIGRP for R1 Rl config router eigrp 1 R1 config router network 192 168 0 0 0 0 0 127 R1 config router network 192 168 0 252 0 0 0 3 R1 config router network 192 168 1 0 R1 config router no auto summary Configure E
3. 92 168 1 0 255 255 255 0 default router 192 168 1 1 ip dhcp pool R1G0 network 192 168 0 0 255 255 255 128 default router 192 168 11 1 Part 3 Troubleshoot DHCPv4 Issues After configuring routers R1 and R2 with DHCPv4 settings several errors in the DHCP configurations were introduced and resulted in connectivity issues R2 is configured as a DHCP server For both pools of DHCP addresses the first nine addresses are reserved for the routers and switches R1 relays the DHCP information to all the R1 LANs Currently PC A and PC B have no access to the network Use the show and debug commands to determine and correct the network connectivity issues Step 1 Record IP settings for PC A and PC B a For PC A and PC B at the command prompt enter ipconfig all to display the IP and MAC addresses b Record the IP and MAC addresses in the table below The MAC address can be used to determine which PC is involved in the debug message IP Address Subnet Mask MAC Address PC A PC B Step 2 Troubleshoot DHCP issues for the 192 168 1 0 24 network on router R1 Router R1 is a DHCP relay agent for all the R1 LANs In this step only the DHCP process for the 192 168 1 0 24 network will be examined The first nine addresses are reserved for other network devices such as routers switches and servers a Use a DHCP debug command to observe the DHCP process on R2 router 2013 Cisco and or its affiliates All ri
4. Ajaj CISCO Cisco Networking Academy Mind Wide Oper a Lab Troubleshooting DHCPv4 Topology S0 0 0 0 0 1 DCE 0 0 0 50 0 1 Internet 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public Page 1 of 8 Lab Troubleshooting DHCPv4 Addressing Table Device Interface IP Address Subnet Mask Default Gateway R1 G0 0 192 168 0 1 255 255 255 128 N A GO 1 192 168 1 1 255 255 255 0 N A S0 0 0 DCE 192 168 0 253 255 255 255 252 N A R2 S0 0 0 192 168 0 254 255 255 255 252 N A S0 0 1 DCE 209 165 200 226 255 255 255 252 N A ISP S0 0 1 209 165 200 225 255 255 255 252 N A S1 VLAN 1 192 168 1 2 255 255 255 0 192 168 1 1 S2 VLAN 1 192 168 0 2 255 255 255 128 192 168 0 1 PC A NIC DHCP DHCP DHCP PC B NIC DHCP DHCP DHCP Objectives Part 1 Build the Network and Configure Basic Device Settings Part 2 Troubleshoot DHCPv4 Issues Background Scenario The Dynamic Host Configuration Protocol DHCP is a network protocol that lets the network administrators manage and automate the assignment of IP addresses Without DHCP the administrator must manually assign and configure IP addresses preferred DNS servers and the default gateway As the network grows in size this becomes an administrative problem when devices are moved from one internal network to another In this scenario the company has grown in size and the ne
5. D htype 1 chaddr 0050 56be 768c Mar 5 06 32 16 939 DHCPD circuit id 00000000 Mar 5 06 32 16 943 DHCPD Allocated binding 2944C764 Mar 5 06 32 16 943 DHCPD Adding binding to radix tree 192 168 1 1 Mar 5 06 32 16 943 DHCPD Adding binding to hash tree Mar 5 06 32 16 943 DHCPD assigned IP address 192 168 1 1 to client 0100 5056 be76 8c ue aaa Mar 5 06 32 16 951 DHCPD Sending notification of DISCOVER Mar 5 06 32 16 951 DHCPD htype 1 chaddr 0050 56be 768c Mar 5 06 32 16 951 DHCPD circuit id 00000000 Mar 5 06 32 1 R2 6 951 DHCPD Seeing if there is an internally specified pool class Mar 5 06 32 16 951 DHCPD htype 1 chaddr 0050 56be 768c Mar 5 06 32 16 951 DHCPD circuit id 00000000 Mar 5 06 32 16 951 DHCPD Allocated binding 31DC93C8 Mar 5 06 32 16 951 DHCPD Adding binding to radix tree 192 168 1 2 Mar 5 06 32 16 951 DHCPD Adding binding to hash tree 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public Page 5 of 8 Lab Troubleshooting DHCPv4 Mar 5 06 32 16 951 DHCPD assigned IP address 192 168 1 2 to client a Mar 5 06 32 18 383 DHCPD returned 192 168 1 2 to address pool R1G1 Mar 5 06 32 18 383 DHCPD Sending notification of DISCOVER Mar 5 06 332 18 383 DHCPD htype 1 chaddr 0050 56be 6c89 Mar 5 06 32 18 383 DHCPD circuit id 00000000 Mar 5 06 32 18 383 DHCPD Seeing if there is an internally specified pool cla
6. IGRP and a static default route on R2 R2 config router eigrp 1 R2 config router network 192 168 0 252 0 0 0 3 R2 config router redistribute static R2 config router exit R2 config ip route 0 0 0 0 0 0 0 0 209 165 200 225 Configure a summary static route on ISP to the networks on R1 and R2 routers ISP config ip route 192 168 0 0 255 255 254 0 209 165 200 226 Step 4 Verify network connectivity between the routers If any pings between the routers fail correct the errors before proceeding to the next step Use show ip route and show ip interface brief to locate possible issues Step 5 Configure basic settings for each switch a Disable DNS lookup 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public Page 3 of 8 Lab Troubleshooting DHCPv4 Configure device name as shown in the topology Configure the IP address for the VLAN 1 interface and the default gateway for each switch Assign class as the privileged EXEC mode password Assign cisco as the console and vty passwords Oo o20 5 Configure logging synchronous for the console line Step 6 Verify the hosts are configured for DHCP Step 7 Load the initial DHCP configuration for R1 and R2 Router R1 interface GigabitEthernet0 1 ip helper address 192 168 0 253 Router R2 ip dhcp excluded address 192 168 11 1 192 168 11 9 ip dhcp excluded address 192 168 0 1 192 168 0 9 ip dhcp pool R1G1 network 1
7. ces the router has There is no way to effectively list all the combinations of configurations for each router class This table includes identifiers for the possible combinations of Ethernet and Serial interfaces in the device The table does not include any other type of interface even though a specific router may contain one An example of this might be an ISDN BRI interface The string in parenthesis is the legal abbreviation that can be used in Cisco IOS commands to represent the interface 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public Page 8 of 8
8. ddress from the DHCP server Record the assigned IP address and default gateway information The process can be observed in the debug message on R2 Mar 5 06 50 11 863 DHCPD Sending notification of DISCOVER Mar 5 06 50 11 863 DHCPD htype 1 chaddr 0050 56be 768c Mar 5 06 50 11 863 DHCPD circuit id 00000000 Mar 5 06 50 11 863 DHCPD Seeing if there is an internally specified pool class 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public Page 6 of 8 Lab Troubleshooting DHCPv4 Mar 5 06 50 11 863 DHCPD htype 1 chaddr 0050 56be 768c Mar 5 06 50 11 863 DHCPD circuit id 00000000 Mar 5 06 50 11 863 DHCPD requested address 192 168 1 3 has already been assigned Mar 5 06 50 11 863 DHCPD Allocated binding 3003018C Mar 5 06 50 11 863 DHCPD Adding binding to radix tree 192 168 1 10 Mar 5 06 50 11 863 DHCPD Adding binding to hash tree Mar 5 06 50 11 863 DHCPD assigned IP address 192 168 1 10 to client 0100 5056 be76 8c lt output omitted gt Verify network connectivity Can PC A ping the assigned default gateway Can PC A ping the R2 router Can PC A ping the ISP router Step 3 Troubleshoot DHCP issues for 192 168 0 0 25 network on R1 Router R1 is a DHCP relay agent for all the R1 LANs In this step only the DHCP process for the 192 168 0 0 25 network is examined The first nine addresses are reserved for other network devices a Use a
9. ghts reserved This document is Cisco Public Page 4 of 8 Lab Troubleshooting DHCPv4 R2 debug ip dhcp server events b On R1 display the running configuration for the GO 1 interface R1 show run interface g0 1 interface GigabitEthernet0 1 ip address 192 168 1 1 255 255 255 0 ip helper address 192 168 0 253 duplex auto speed auto If there are any DHCP relay issues record any commands that are necessary to correct the configurations errors c Inacommand prompt on PC A type ipconfig renew to receive an address from the DHCP server Record the configured IP address subnet mask and default gateway for PC A d Observe the debug messages on R2 router for the DHCP renewal process for PC A The DHCP server attempted to assign 192 168 1 1 24 to PC A This address is already in use for G0 1 interface on R1 The same issue occurs with IP address 192 168 1 2 24 because this address has been assigned to S1 in the initial configuration Therefore an IP address of 192 168 1 3 24 has been assigned to PC A The DHCP assignment conflict indicates there may be an issue with the excluded address statement on the DHCP server configuration on R2 Mar 5 06 32 16 939 DHCPD Sending notification of DISCOVER Mar 5 06 32 16 939 DHCPD htype 1 chaddr 0050 56be 768c Mar 5 06 32 16 939 DHCPD circuit id 00000000 Mar 5 06 32 16 939 DHCPD Seeing if there is an internally specified pool class Mar 5 06 32 16 939 DHCP
10. ng the DHCP assigned default gateway Can PC B ping its default gateway 192 168 0 1 Can PC B ping the R2 router Can PC B ping the ISP router f If any issues failed in Step e record the problems and any commands to resolve the issues lease time remaining DHCPD htype 1 chaddr 0050 56be f6db DHCPD secs 86400 Release and renew the IP configurations on PC B Repeat Step e to verify network connectivity h Discontinue the debug process by using the undebug all command R2 undebug all All possible debugging has been turned off Reflection What are the benefits of using DHCP Router Interface Summary Table Router Interface Summary Router Model Ethernet Interface 1 Ethernet Interface 2 Serial Interface 1 Serial Interface 2 1800 Fast Ethernet 0 0 Fast Ethernet 0 1 Serial 0 0 0 S0 0 0 Serial 0 0 1 S0 0 1 F0 0 F0 1 1900 Gigabit Ethernet 0 0 Gigabit Ethernet 0 1 Serial 0 0 0 S0 0 0 Serial 0 0 1 S0 0 1 G0 0 G0 1 2801 Fast Ethernet 0 0 Fast Ethernet 0 1 Serial 0 1 0 S0 1 0 Serial 0 1 1 S0 1 1 F0 0 F0 1 2811 Fast Ethernet 0 0 Fast Ethernet 0 1 Serial 0 0 0 S0 0 0 Serial 0 0 1 S0 0 1 F0 0 F0 1 2900 Gigabit Ethernet 0 0 Gigabit Ethernet 0 1 Serial 0 0 0 S0 0 0 Serial 0 0 1 S0 0 1 G0 0 G0 1 Note To find out how the router is configured look at the interfaces to identify the type of router and how many interfa
11. ss Mar 5 06 32 18 383 DHCPD htype 1 chaddr 0050 56be 6c89 Mar 5 06 32 18 383 DHCPD circuit id 00000000 Mar 5 06 32 18 383 DHCPD Allocated binding 2A40E074 Mar 5 06 32 18 383 DHCPD Adding binding to radix tree 192 168 1 3 Mar 5 06 32 18 383 DHCPD Adding binding to hash tree lt output omitted gt e Display the DHCP server configuration on R2 The first nine addresses for 192 168 1 0 24 network are not excluded from the DHCP pool R2 show run section dhcp ip dhcp excluded address 192 168 11 1 192 168 11 9 ip dhcp excluded address 192 168 0 1 192 168 0 9 ip dhcp pool R1G1 network 192 168 1 0 255 255 255 0 default router 192 168 1 1 ip dhcp pool R1G0 network 192 168 0 0 255 255 255 128 default router 192 168 1 1 Record the commands to resolve the issue on R2 f At the command prompt on PC A type ipconfig release to return the 192 168 1 3 address back to the DHCP pool The process can be observed in the debug message on R2 Mar 5 06 49 59 563 DHCPD Sending notification of TERMINATION Mar 5 06 49 59 563 DHCPD address 192 168 1 3 mask 255 255 255 0 Mar 5 06 49 59 563 DHCPD reason flags RELEASE Mar 5 06 49 59 563 DHCPD htype 1 chaddr 0050 56be 768c Mar 5 06 49 59 563 DHCPD lease time remaining secs 85340 Mar 5 06 49 59 563 DHCPD returned 192 168 1 3 to address pool RIGI g Atthe command prompt on PC A type ipconfig renew to be assigned a new IP a
12. twork administrators can no longer assign IP addresses to devices manually The R2 router has been configured as a DHCP server to assign IP addresses to the host devices on router R1 LANs Several errors in the configuration have resulted in connectivity issues You are asked to troubleshoot and correct the configuration errors and document your work Ensure that the network supports the following 1 The router R2 should function as the DHCP server for the 192 168 0 0 25 and 192 168 1 0 24 networks connected to R1 2 All PCs connected to S1 and S2 should receive an IP address in the correct network via DHCP Note The routers used with CCNA hands on labs are Cisco 1941 Integrated Services Routers ISRs with Cisco IOS Release 15 2 4 M3 universalk9 image The switches used are Cisco Catalyst 2960s with Cisco IOS Release 15 0 2 lanbasek9 image Other routers switches and Cisco IOS versions can be used Depending on the model and Cisco IOS version the commands available and output produced might vary from what is shown in the labs Refer to the Router Interface Summary Table at the end of this lab for the correct interface identifiers Note Make sure that the routers and switches have been erased and have no startup configurations If you are unsure contact your instructor Required Resources 2013 Cisco and or its affiliates All rights reserved This document is Cisco Public e 3 Routers Cisco 1941 with Cisco IOS Release 15 2 4 M
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