Designing and Implementing Linux Firewalls and QoS using netfilter, iproute2, NAT and l7-filter PDF

The author draws on his experience to offer the reader valuable advice on the best practices. Providing only necessary theoretical background, the book takes a practical approach, presenting case studies and plenty of illustrative examples. This book is aimed at Linux Network administrators<!--[if !supportAnnotations]--> with some understanding of Linux security threats and issues, or any one interested in securing their systems behind a firewall. Basic knowledge of Linux is presumed but other than that this book shows you how to do the rest, from configuring your system to dealing with security breaches.