9. Debugging the Firewall Rules

So now the firewall is set up, installed, and activated. But nothing works! You’re locked out. Who knows what’s going on? Now what? Where do you even begin?

Firewall rules are notoriously difficult to get right. If you’re developing by hand, bugs will invariably crop up. Even if you produce a firewall script with an automatic firewall-generation tool, your script undoubtedly will require customized tweaking eventually.

This chapter introduces additional reporting features of the iptables and nftables tools and other system tools. The information is invaluable when debugging your firewall rules. This chapter explains what the information can tell you about your firewall.

General Firewall Development Tips

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