Chapter 9. Diagnostics

The intent of this chapter is to provide general technical guidance for troubleshooting firewall problems that this book does not directly cover in Section III. We have taken great pains in Section III to research some of the most common and not so common problems users have encountered with iptables firewalls, but we cannot cover every possible protocol or configurationhence the purpose of this chapter. It is our hope that this chapter provides enough info about how we diagnose new and fabulously obscure problems with the firewalls we build. We've been able to solve every problem so far by applying a solid troubleshooting methodology and by using these techniques and tools.