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 currently works writing and creating certification tools. He is the author of all the previous books in the Cisco Press CCNA Official Certification Guide series, as well as author of the CCNP ROUTE 642-902 Official Certification Guide, the QoS 642-642 Exam Certification Guide, and co-author of the CCIE Routing and Switch Official Certification Guide and several other titles. He is also a consultant for the CCNA 640-802 Network Simulator from Pearson and for a forthcoming replacement version of that product. He maintains study tools, links to his blogs, and other resources at http://www.certskills.com.