CCNA Study Guide Chapter 3 Summary

This chapter began with a review of Layer 2 switching. This included a look at how a switch segments a network into a number of smaller collision domains, as well as how a switch makes full duplex communication possible.

This was followed by a look at the different switching methods support by Cisco including Store-and-Forward, Cut-Through, and the default for the Cisco 1900 series, FragmentFree.

A look at redundancy and loop avoidance explained the benefits of having multiple paths on a bridged or switched network, but also the potential problems this introduces, namely broadcast storms. The process by which a broadcast storm happens was also discussed step by step.

Loop avoidance for bridged networks was covered in an overview of the Spanning Tree protocol. The process by which switches elect a Root Bridge, choose Root Ports and Designated Ports were also illustrated with examples. The four Spanning Tree port states – Listening, Learning, Blocking, and Forwarding – were also discussed.

A look at VLANs provided an overview of the benefits they provide in segmenting a network into multiple broadcast domains in a switched environment. The VLAN Trunking Protocol (VTP) was introduced as a way to easily configure VLANs on switches across a VTP management domain. VTP Pruning was also discussed.

Trunking techniques included a look at tagging protocols such as Inter Switch Linking (ISL), a Cisco proprietary protocol for VLAN identification.

Author: Dan DiNicolo

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