Book excerpt: Harden perimeter routers with Cisco firewall functionality and features to ensure network security Detect and prevent denial of service (DoS) attacks with TCP Intercept, Context-Based Access Control (CBAC), and rate-limiting techniques Use Network-Based Application Recognition (NBAR) to detect and filter unwanted and malicious traffic Use router authentication to prevent spoofing and routing attacks Activate basic Cisco IOS filtering features like standard, extended, timed, lock-and-key, and reflexive ACLs to block various types of security threats and attacks, such as spoofing, DoS, Trojan horses, and worms Use black hole routing, policy routing, and Reverse Path Forwarding (RPF) to protect against spoofing attacks Apply stateful filtering of traffic with CBAC, including dynamic port mapping Use Authentication Proxy (AP) for user authentication Perform address translation with NAT, PAT, load distribution, and other methods Implement stateful NAT (SNAT) for redundancy Use Intrusion Detection System (IDS) to protect against basic types of attacks Obtain how-to instructions on basic logging and learn to easily interpret results Apply IPSec to provide secure connectivity for site-to-site and remote access connections Read about many, many more features of the IOS firewall for mastery of router security The Cisco IOS firewall offers you the feature-rich functionality that you've come to expect from best-of-breed firewalls: address translation, authentication, encryption, stateful filtering, failover, URL content filtering, ACLs, NBAR, and many others. Cisco Router Firewall Security teaches you how to use the Cisco IOS firewall to enhance the security of your perimeter routers and, along the way, take advantage of the flexibility and scalability that is part of the Cisco IOS Software package. Each chapter in Cisco Router Firewall Security addresses an important component of perimeter router security. Author Richard Deal explains the advantages and disadvantages of all key security features to help you understand when they should be used and includes examples from his personal consulting experience to illustrate critical issues and security pitfalls. A detailed case study is included at the end of the book, which illustrates best practices and specific information on how to implement Cisco router security features. Whether you are looking to learn about firewall security or seeking how-to techniques to enhance security in your Cisco routers, Cisco Router Firewall Security is your complete reference for securing the perimeter of your network. This book is part of the Networking Technology Series from Cisco Press, which offers networking professionals valuable information for constructing efficient networks, understanding new technologies, and building successful careers.