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Sams Teach Yourself Network Troubleshooting in 24 Hours, Second Edition by Jonathan Feldman

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NAT Problems

NAT can be a major bummer if you’re trying to play multiplayer games. Sometimes, this is because the games embed your IP address inside the application payload. There’s nothing that a NAT firewall can do about this at layer 3; you would need an application-aware firewall.

What happens when NAT gets embedded in an app payload? Well, the application ignores layer 3 information in the packet and decides to try to contact the network address within the payload. Clearly, this isn’t happening if you are using private (RFC 1918) addresses—the Internet will refuse to route them (see Figure 22.4).

Figure 22.4. NAT and an application that just won’t listen to the layer 3 information.

What else might happen? If you have two workstations ...

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