Introduction

5.0.1

Why should I take this module?

Welcome to STP Concepts!

A well-designed Layer 2 network will have redundant switches and paths to ensure that if one switch goes down, another path to a different switch is available to forward data. Users of the network would not experience any disruption of service. Redundancy in a hierarchical network design fixes the problem of a single point of failure, yet it can create a different kind of problem called Layer 2 loops.

What is a loop? Imagine that you are at a concert. The singer’s microphone and the amplified loudspeaker can, for a variety of reasons, create a feedback loop. What you hear is an amplified signal from the microphone that comes out of the loudspeaker which is then picked up again by the microphone, amplified further, and passed again through the loudspeaker. The sound quickly becomes very loud, unpleasant, and makes it impossible to hear any actual music. This continues until the connection between the microphone and the loudspeaker is cut.

A Layer 2 loop creates similar chaos in a network. It can happen very quickly and make it impossible to use the network. There are a few common ways that a Layer 2 loop can be created and propagated. Spanning Tree Protocol (STP) is designed specifically to eliminate Layer 2 loops in your network. This module discusses causes of loops and the various types of spanning tree protocols. It includes a video and a Packet Tracer activity to help you understand STP concepts.

What will I learn to do in this module?

Module Title: STP Concepts

Module Objective: Explain how STP enables redundancy in a Layer 2 network.

Table caption
Topic Title Topic Objective
Purpose of STP Explain common problems in a redundant, L2 switched network.
STP Operations Explain how STP operates in a simple switched network.
Evolution of STP Explain how Rapid PVST+ operates.

 

 

Purpose of STP