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

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Top-Secret Definitions

Let’s lay out some definitions here. When most folks talk about firewalls, they usually mean packet-filtering routers. As you learned in Hour 1, “Understanding Networking: The Telephone Analogy,” a router is the glue between two or more network segments. (We discussed routers in depth in Hour 15, “Home and Office Routers.”) Therefore, a packet-filtering router refers to a router that has rules about who and what is allowed to be routed between its interfaces. Not so bad, huh?

What’s a proxy server? First of all, it’s not any kind of router. So what is it? Like any kind of server, a proxy server offers services. It’s basically a multihomed server that accepts requests on a certain port and forwards these requests to a server ...

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