Figure 1 shows R2 enabled for PAT, using the range of addresses 209.165.200.226 to 209.165.200.240.
When there are IPv4 connectivity problems in a NAT environment, it is often difficult to determine the cause of the problem. The first step in solving the problem is to rule out NAT as the cause. Follow these steps to verify that NAT is operating as expected:
Step 1. Based on the configuration, clearly define what NAT is supposed to achieve. This may reveal a problem with the configuration.
Step 2. Verify that correct translations exist in the translation table using the show ip nat translations command.
Step 3. Use the clear and debug commands to verify that NAT is operating as expected. Check to see if dynamic entries are recreated after they are cleared.
Step 4. Review in detail what is happening to the packet, and verify that routers have the correct routing information to move the packet.
Figure 2 shows the output of the show ip nat statistics and show ip nat translations commands. Prior to using the show commands, the NAT statistics and entries in the NAT table are cleared with the clear ip nat statistics and clear ip nat translation * commands. After the host at 192.168.10.10 Telnets to the server at 209.165.201.1, the NAT statistics and NAT table are displayed to verify NAT is working as expected.
In a simple network environment, it is useful to monitor NAT statistics with the show ip nat statistics command. The show ip nat statistics command displays information about the total number of active translations, NAT configuration parameters, the number of addresses in the pool, and the number that have been allocated. However, in a more complex NAT environment, with several translations taking place, this command may not clearly identify the issue. It may be necessary to run debug commands on the router.