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Verification of NAT Translation 351
Because this is a simple translation, only the information that is relevant is put into the table.
The concept of outside local and outside global is not used, and therefore not presented when a
simple NAT translation is configured. If an overloaded translation has been configured, the
output from the show ip nat translation command would be as demonstrated in Example 11-7.
Notice that the Outside Local address and the Outside Global address are the same. Because the
router is not performing an overlapped configuration, the Outside Global address is not known.
When an overlapping configuration is being used, the router has knowledge of the Outside
Global address, so the output from a show ip nat translation command would appear as
demonstrated in Example 11-8.
Because the router is performing both translations, the Outside Global address is known.
The show ip nat statistics command is also useful in troubleshooting a NAT installation, as
demonstrated in Example 11-9.
The show ip nat statistics command displays which interfaces are inside and which are outside,
the pool name, and the addresses that are with the mask. The hits and misses refer to the number
of times a translation lookup succeeded or failed.
Example 11-7
NAT Overloaded Translation Output
Pro Inside global Inside local Outside local Outside global
tcp 143.4.23.1:1098 10.1.0.1:1098 73.4.5.6:23 73.4.5.6:23
tcp 143.4.23.1:1345 10.1.0.2:1345 73.4.5.6:23 73.4.5.6:23
tcp 143.4.23.1:1989 10.1.0.3:1989 73.4.5.7:21 73.4.5.7:21
Example 11-8
NAT Overlapping Translation Output
Pro Inside global Inside local Outside local Outside global
tcp 133.3.3.1:1098 10.1.0.1:1098 173.4.5.6:23 10.1.0.23:23
tcp 133.3.3.2:1345 10.1.0.2:1345 173.4.5.6:23 10.1.0.23:23
tcp 133.3.3.3:1989 10.1.0.3:1989 173.4.5.7:21 10.2.0.45:21
Example 11-9
Troubleshooting NAT Installation with show ip nat statistics
Router#show ip nat statistics
Total translations: 1 (0 static, 1 dynamic; 0 extended)
Outside interfaces: Serial0Inside interfaces: Ethernet0Hits: 1 Misses: 0
Expired translations: 2Dynamic mappings:-- Inside Source
access-list 1 pool my-pool refcount 2 pool my-pool: netmask 255.255.255.0
start 172.3.4.1 end 172.3.4.7
type generic, total addresses 7, allocated 1 (14%), misses 0