Learn more Do more: CCNA: Cisco Certified Network Associate Study Guide, Third Edition

A hub forwards all packets to all ports while a switch learns to associate MAC addresses with ports to make more efficient one-to-one connections. This is one of the less arcane facts you'll learn from this study guide. Here's a more arcane one: The available cable ends for Cisco routers are EITA/TIA-232, EIA/TIA-449, V.35(for CSU/DSU), X.21(for X.25) and EIA-530. Pay close attention because you will be tested. An example multi-choice question asks, "What Cisco layer provides segmentation of contention networks?". Your choices are Access, Physical, Network, Distribution, Core, Transport, Data link.

This study guide highlights the differences between internetworking as a theoretical study and its implementation in the real world. This is the activity for which Cisco sells routers, hubs and switches. Reading this guide to is to glimpse the elephant on whose back rests the virtual world. It's fascinating and hermetic. It contains the spells the Net wizards use to abolish distance.

Like all magic, it is both precise and arbitrary. While 10Base2 can support a bus up to 185m long with 30 hosts 10Base5 can run to 500m and 208 users. But not 501m or 209 hosts because then the magic won't work. This is an excellent study guide for those who find hardcore technology capable of handling millions of events in tiny slivers of a second with utter reliability for months on end utterly fascinating.

Read the section on how the spanning tree protocol prevents network loops forming. By the way, did you know IEEE 802.1d STP supported by Cisco is incompatible with inventor DEC's version? You will. --Steve Patient --This text refers to an out of print or unavailable edition of this title.

Synopsis
The Cisco Certified Network Associate certification (640-607) is the first-tier certification in Cisco's Network Support and Communications and Services tracks. The CD includes a fully functional router simulator with lab exercises to help candidates prepare for Cisco's simulation question format.