, 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 author of all the previous editions of the CCNA Exam Certification Guides from Cisco Press, as well as the CCNP ROUTE 642-902 Official Certification Guide, the CCIE Routing and Switching Official Exam Certification Guide, Computer Networking First Step, the CCNA Video Mentor, and other titles. He is also the primary networking consultant for the CCNA 640-802 Network Simulator.