Chapter 13. Troubleshooting Firewalls

One of the more difficult skills to cultivate is how to troubleshoot problems related to your firewall or firewall implementation. The reason for this difficulty is that firewalls, by design, tend to do some pretty significant manipulation of network traffic, thus making it difficult to determine whether whatever anomaly you are seeing is an actual problem or a design of the firewall. For example, so many firewalls are designed by default to not respond to Internet Control Message Protocol (ICMP) ping packets. Therefore, if you attempt to ping the firewall to troubleshoot a problem and you do not get a response, it can be difficult to determine whether the lack of a response is indeed a problem or actually ...

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