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TCP/IP Guide by Charles M. Kozierok

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IP NAT Compatibility Issues and Special Handling Requirements

In a perfect world NAT could be made transparent to the devices using it. We would like to be able to have a NAT router change IP addresses in request datagrams as they leave the network and change them back in responses that come back, and have none of the hosts be any wiser. Unfortunately, this isn't a perfect world.

Operation of Overlapping NAT/Twice NAT This figure is very similar to , except that as you can see, the NAT router translates both source and destination addresses each time (shown in bold). contains a complete explanation of the four steps in overlapping NAT. Refer to for an explanation of address types.

Figure 28-5. Operation of Overlapping NAT/Twice NAT This figure is very similar to Figure 28-2, except that as you can see, the NAT router translates both source and destination addresses each time (shown in bold). Table 28-4 contains a complete explanation of the four steps ...

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