Wendell Odom, CCIE No. 1624, has been in the networking industry since 1981. He has worked as a network engineer, consultant, systems engineer, instructor, and course developer. He is author of all the previous editions of the CCNA Exam Certification Guide series from Cisco Press, as well as the Cisco QoS Exam Certification Guide, the CCIE Routing and Switching Official Exam Certification Guide, Computer Networking First Step, the CCNA Video Mentor, and other titles. He also teaches classes for Skyline Advanced Technology Services and blogs regularly on the NetworkWorld.com Cisco Subnet site.