How to Troubleshoot and Verify NAT Configuration
The most common mistake in troubleshooting is not the inability to use commands but the laxity in the examination of entries and configuration. Solving network problems requires careful and proper examination of routing entries and configuration.
There are several useful router commands to verify NAT translations. Cisco routers are equipped with NAT verifying tools.
1. The command: show ip nat translations display the details of NAT assignments; it will enable you to verify that correct translations exist in the translation table. It’s recommended that you clear any dynamic NAT translation entries that might still be on the router.
2. To view additional details about each translation us the following command;
R1#show ip nat translations verbose
This command will display additions information, which includes creation dates and usage of each translation.
To clear NAT translations use the command: clear ip nat translation
R1#clear ip nat translation
3. Verify the operation of NAT by checking details about every packet that is translated by the router. To view this information using the:
R1#debug ip nat or
R1#debug ip nat detailed
The later command debug ip nat detailed Provide a description of each packet that had been considered for translation. It also displays information on some errors such as failure to assign a global IP address.
4. The show ip nat statistics command display:
i, details of all the active translation entries
ii NAT configuration parameters
iii number of IP addresses in the pool
iv total number of assigned IP addresses.
Another useful command for NAT verification is the show run command. With this command, you can view them;
i access command lists
ii interfaces and other configurations
The most common mistake in troubleshooting is not the inability to use commands but the laxity in the examination of entries and configuration.