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350 Chapter 11: Scaling IP Addresses with NAT
The configuration is straightforward. Any packet that arrives at Company A's Internet router,
which has a destination for the 188.88.88.88 host, is translated in a rotary fashion to one of the
four mirrored servers. The configuration in Example 11-5 shows the syntax for this
implementation.
You should note that the declaration statement for the translation specifies that the destination
address should be checked against list 1, not the source address as in previous configurations.
In addition, the argument rotary is placed at the end of the declaration. In this fashion, each
incoming packet is translated to one of the pool members in a recurring sequential fashion; thus,
a load distribution is achieved over the four servers.
You should note that the router does not keep track of the availability of the destination
addresses assigned to it in the "pool"; hence, any change to the number of rotary members or
the internal configuration must be reflected in the router definitions.
Verification of NAT Translation
There are two commands to verify and troubleshoot the NAT configuration: show ip nat
translation
and show ip nat statistics. The translation table is the same format for simple,
overload, overlapped, and load distribution. The information provided is different depending
upon the configuration. Example 11-6 shows the output for a simple translation.
Example 11-5
NAT TCP Load Distribution Implementation
!declare the pool
ip nat pool company-A 188.88.88.1 188.88.88.4 prefix-length 24
!declare the translation
ip nat outside destination list 1 pool company-A rotary
!declare the access-list for translation candidates
access-list 1 permit 188.88.88.88 0.0.0.0
!declare the interfaces
interface S0
ip nat outside
interface E0
ip nat inside
Example 11-6
Verifying NAT Translation
Router#show ip nat translation
Pro Inside global Inside local Outside local Outside global
--- 156.8.34.1 10.15.0.1 --- ---
--- 156.8.34.2 10.15.0.2 --- ---
--- 156.8.34.3 10.15.0.3 --- ---