Lab 1.1.6 Troubleshooting NAT and PAT
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1. yes no Type n and then press Enter The responding line prompt will be Proceed with reload confirm Press Enter to confirm In the first line of the response will be Reload requested by console After the router has reloaded the line prompt will be Would you like to enter the initial configuration dialog yes no Type n and then press Enter The responding line prompt will be Press RETURN to get started Press Enter Now the router is ready for the assigned lab to be performed CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc Router Ethernet Ethernet 1700 FastEthernet r FastEthernet as Serial 0 ee Serial 1 EG 2500 Ethernet 0 EO Ethernet 1 E1 Serial 0 SO Serial 1 S1 2600 FastEthernet 0 0 FA0 0 FastEthernet 0 1 FA0 1 Serial 0 0 S0 0 Serial 0 1 S0 1 In order to find out exactly how the router is configured look at the interfaces This will identify what type and how many interfaces the router has There is no way to effectively list all of the combinations of configurations for each router class What is provided are the identifiers for the possible combinations of interfaces in the device This interface chart 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 an IOS command to represent the interface2. a From the attached hosts ping the FastEthernet interface of the default gateway router b Was the ping from the first host successful c Was the ping from the second host successful d Ifthe answer is no for either question troubleshoot the router and host configurations to find the error Then ping again until they both are successful Step 5 Create a static route a Create a static route from the ISP to the Gateway router Addresses 199 99 9 32 30 have been allocated for Internet access outside of the company Use the ip route command to create the static route ISP config ip route 199 99 9 32 255 255 255 252 200 2 2 18 b Is the static route in the routing table c What command checks the routing table contents d Ifthe route was not in the routing table give one reason why this might be so 2 7 CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc Step 6 Create a default route a Adda default route using the ip route command from the Gateway router to the ISP router This will forward any unknown destination address traffic to the ISP Gateway config ip route 0 0 0 0 0 0 0 0 200 2 2 17 b Is the static route in the routing table c Try to ping from one of the workstations to the ISP serial interface IP address d Was the ping successful e Why Step 7 Define the pool of usable public IP addresses To define the pool of public addresses use the ip nat pool command Gatewa
3. config hostname Gateway Gateway config enable password cisco Gateway config enable secret class Gateway config line console 0 Gateway config line password cisco Gateway config line login Gateway config line exit Gateway config line vty 0 4 Gateway config line password cisco Gateway config line login Gateway config line exit Gateway config interface fastethernet 0 Gateway config 1if ip add 10 10 10 1 255 255 255 0 Gateway config if no shutdown Gateway config if exit Gateway config interface serial 0 Gateway config if ip add 200 2 2 18 255 255 255 252 Gateway config if no shutdown NNN NNN mmm imam am ams Gateway config ip route 0 0 0 0 0 0 0 0 200 2 2 17 5 7 CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc Erasing and reloading the router Enter into the privileged EXEC mode by typing enable If prompted for a password enter class if that does not work ask the instructor Router gt enable At the privileged EXEC mode enter the command erase startup config Router erase startup config The responding line prompt will be Erasing the nvram filesystem will remove all files Continue confirm Press Enter to confirm The response should be Erase of nvram complete Now at the privileged EXEC mode enter the command reload Router config reload The responding line prompt will be System configuration has been modified Save
4. 7 7 CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc
5. Cisco SYSTEMS Router 1 Router 2 Router Router FastEthernet 0 Address Interface Serial 0 Address Loopback 0 Address Enable Secret Enable VTY Con Designation Name Subnet Mask Type Subnet Mask Subnet Mask Password sole Passwords Straight through cable Serial cable EE a a Console rollover EEEEETETETETITITETIT Crossover cable O O Objective e Configure a router for Network Address Translation NAT and Port Address Translation PAT e Troubleshoot NAT and PAT using debug Background Preparation The ISP has allocated a company the public CIDR IP address 199 99 9 32 30 This is equivalent to four public IP addresses Since the company has an internal requirement for more than 30 addresses the IT manager has decided to use NAT with PAT Routing between the ISP and the gateway router is done using a static route between the ISP and the gateway and a default route between the gateway and the ISP The ISP connection to the Internet will be represented by a loopback address on the ISP router Cable a network similar to the one in the diagram above Any router that meets the interface requirements displayed on the above diagram may be used This includes the following and any of their possible combinations e 800 series routers e 1600 series routers e 1 00 series routers e 2500 series routers e 2600 series routers 1 7 CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc
6. Please refer to the chart at the end of the lab to correctly identify the interface identifiers to be used based on the equipment in the lab The configuration output used in this lab is produced from 1721 series routers Any other router used may produce slightly different output Conduct the following steps on each router unless specifically instructed otherwise Start a HyperTerminal session Note Refer to the erase and reload instructions at the end of this lab Perform those steps on all routers in this lab assignment before continuing Step 1 Configure the routers Configure all of the following according to the chart e The hostname e The console password e The virtual terminal password e The enable secret password e The interfaces If problems occur during this configuration refer to Lab 1 1 4a Configuring NAT Step 2 Save the configuration At the privileged EXEC mode prompt on both routers type the command copy running config startup config Step 3 Configure the hosts with the proper IP address subnet mask and default gateway Each workstation should be able to ping the attached router If the ping was not successful troubleshoot as necessary Check and verify that the workstation has been assigned a specific IP address and default gateway If running Windows 98 check using Start gt Run gt winipcfg If running Windows 2000 or higher check using ipconfig in a DOS window Step 4 Verify that the network is functioning
7. ns ping 172 16 1 1 Ifthe ip nat outside statement was entered correctly there should be output from the debug ip nat command d What does the line NAT S 10 10 10 gt 199 99 9 33 mean e To stop the debug output type undebug all at the privileged EXEC mode prompt Upon completion of the previous steps finish the lab by doing the following e Logoff by typing exit e Turn the router off e Remove and store the cables and adapter CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc Configuration reference sheet This sheet contains the basic configuration commands for the ISP and Gateway routers ISP Router configure terminal Router config hostname ISP ISP config enable password cisco ISP config enable secret class ISP config line console 0 ISP config line password cisco ISP config line login ISP config line exit ISP config line vty 0 4 ISP config line password cisco ISP config line login ISP config line exit ISP config interface loopback 0 ISP config if ip add 172 16 1 1 255 255 255 255 ISP config if exit ISP config interface serial 0 ISP config if ip add 200 2 2 17 255 255 255 252 ISP config if no shutdown ISP config 1if celock rate 64000 ISP config ip route 199 99 9 32 255 255 255 252 200 2 2 18 ISP config end ISP copy running config startup config Destination filename startup config Enter Gateway Router configure terminal Router
8. y config ip nat pool public access 199 99 9 32 199 99 9 35 netmask 255 255 255 252 Step 8 Define an access list that will match the inside private IP addresses To define the access list to match the inside private addresses use the access list command Gateway config access list 1 permit 10 10 10 0 0 0 0 255 Step 9 Define the NAT translation from inside list to outside pool To define the NAT translation use the ip nat inside source command Gateway config ip nat inside source list 1 pool public access overload Step 10 Specify the interfaces On the active interfaces on the router it needs to be specified as either inside or outside interfaces with respect to NAT To do this use the ip nat inside command Gateway config interface fastethernet 0 Gateway config if ip nat inside Step 11 Testing the configuration a Turn on debugging for the NAT process by typing debug ip nat atthe privileged EXEC mode prompt b Does the debug command show any output c If translation were taking place there would be output from the debug command While reviewing the running configuration of the gateway router itis seen that the ip nat outside statement has not been entered on the serial 0 interface To configure this enter the following Gateway config interface serial 0 3 7 CCNA 4 WAN Technologies v 3 1 Lab 1 1 6 Copyright 2003 Cisco Systems Inc 4 T Gateway config if ip nat outside From the workstatio
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