28.1.1 Overview

The Spanning Tree Protocol is a Layer 2 loop prevention protocol. The Spanning Tree Protocol can be used to make Layer 2 networks redundant, and prevent loops.

The following figure provides an overview of a network with a Spanning Tree Protocol applied.

Figure 28-1: Overview of networks that apply Spanning Tree Protocols

In the configuration in the diagram, the switches responsible for the network core are made redundant, as are the communication paths from the edge switch handling the terminals. By making the switches and communication paths redundant, transmission can carry over to an alternate path when a fault occurs on the normal communication path.

A Layer 2 loop configuration is one in which a Layer 2 network is made redundant. Layer 2 loops cause broadcast storms and destabilize MAC address learning. Spanning Tree Protocols are protocols that prevent loops on Layer 2 networks in redundant loop configurations, by choosing locations in which to stop communication, and putting them in Blocking status.