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

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Summary

A packet-filtering router with stateful inspection is usually what’s referred to as a firewall. These routers have rules as to what is and is not allowed into a network on a service-by-service basis. Older firewalls don’t allow for NAT or stateful inspection. Small home or office firewalls typically don’t have great logging or stateful features. NAT is famous for breaking certain applications because of embedded IP addresses in the application payload; certain video conferencing and games are good examples.

Proxy servers differ from packet-filtering firewalls in that they operate on OSI layer 7, not layer 3; they act as a workstation on the Internet, and they pass their results back to workstations inside your network. This makes for ...

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