Network Access

Domain 1 taught you what the pieces of a network are. Domain 2 is about the access layer: the switches and wireless access points that end users actually plug into or associate with. Every question in this domain comes back to one idea: how do we connect hundreds of devices to a set of switches and access points, keep their traffic separated where it should be separated, avoid loops, and still let everything reach everything it is supposed to reach?

This domain is 20% of the exam, so expect roughly 20 of your ~100 questions to come from here. The topics are also heavily configuration oriented. Cisco wants you to read a configuration, spot a mistake, and predict what a show command will display. Practice typing every command in this chapter on a simulator such as Packet Tracer; it is the fastest way to make it stick.

A quick map of what you will learn:

• 2.1 VLANs – dividing one physical switch into several logical switches.
• 2.2 Trunks and 802.1Q – carrying many VLANs over a single cable between switches.
• 2.3 CDP and LLDP – protocols that let devices announce who they are to their neighbors.
• 2.4 EtherChannel – bundling several cables into one logical link.
• 2.5 Spanning Tree – the protocol that stops redundant links from causing loops. This is the single biggest topic in the domain.
• 2.6 to 2.9 Wireless – how Cisco wireless LANs are built, cabled, managed, and configured through the controller GUI.