This book works well on a lot of levels, but its careful integration of explanations (statements of applicability and references to standards documents), case studies (usually illustrated with network diagrams), configuration details (input/output listings from Cisco routers), and practical advice (a note on why network address translation isn't much of a barrier against attackers) is key to its success. The illustrators worked overtime, as well, to link Internetwork Operating System (IOS) listings with network diagrams and thereby more effectively illustrate routing behaviors. An excellent index and troubleshooting exercises similar to those on the CCIE practical exam round out this package. --David Wall