31 Days Before Your CCNA Exam

304 31 Days Before Your CCNA ExamThe static entry is always in the table. Currently, there are two dynamic entries. Notice that bothinside clients received the same inside global address, but the port numbers are different.The show ip nat statistics command shown in Example 5-5 displays information about the totalnumber of active translations, NAT configuration parameters, how many addresses are in the pool,and how many have been allocated.Example 5-5Verifying NAT Operations with show ip nat statisticsR2#show ip nat statisticsTotal translations: 3 (1 static, 2 dynamic, 2 extended)Outside Interfaces: Serial0/1/0Inside Interfaces: FastEthernet0/0 , Serial0/0/0 , Serial0/0/1Hits: 29 Misses: 7Expired translations: 5Dynamic mappings:-- Inside Sourceaccess-list 1 pool NAT-POOL1 refCount 2pool NAT-POOL1: netmask 255.255.255.224start 209.165.200.226 end 209.165.200.240type generic, total addresses 3 , allocated 1 (7%), misses 0Alternatively, use the show run command and look for NAT, access command list, interface, orpool-related commands with the required values. Examine the output from these commands carefullyto discover any errors.It is sometimes useful to clear the dynamic entries sooner than the default. This is especially truewhen testing the NAT configuration. To clear dynamic entries before the timeout has expired, usethe clear ip nat translation * privileged EXEC command.Troubleshooting NATWhen you have IP connectivity problems in a NAT environment, it is often difficult to determinethe cause of the problem. The first step in solving your problem is to rule out NAT as the cause.Follow these steps to verify that NAT is operating as expected:Step 1Step 2Step 3Step 4Based on the configuration, clearly define what NAT is supposed to achieve. Thismight reveal a problem with the configuration.Verify that correct translations exist in the translation table using the show ip nattranslations command.Use the clear and debug commands to verify that NAT is operating as expected. Checkto see if dynamic entries are re-created after they are cleared.Review in detail what is happening to the packet, and verify that routers have the correctrouting information to forward the packet.