Reference Guide

Spanning Tree Protocol (STP) | 577

Spanning Tree Protocol (STP)

Overview

The spanning tree protocol (STP) is a Layer 2 protocol—specified by IEEE 802.1d—that eliminates loops

in a bridged topology by enabling only a single path through the network. By eliminating loops, the

protocol improves scalability in a large network and allows you to implement redundant paths, which can

be activated after the failure of active paths. Layer 2 loops, which can occur in a network due to poor

network design and without enabling protocols like xSTP, can cause unnecessarily high switch CPU

utilization and memory consumption.

Table 33-1 lists the variations of STP that FTOS supports.

This chapter contains the following sections:

• Configuring Spanning Tree

• Configuring Interfaces for Layer 2 Mode

• Enabling Spanning Tree Protocol Globally

• Adding an Interface to the Spanning Tree Group

• Removing an Interface from the Spanning Tree Group

• Modifying Global Parameters

• Modifying Interface STP Parameters

• Enabling PortFast

• BPDU Filtering

• STP Root Selection

• STP Root Guard

• SNMP Traps for Root Elections and Topology Changes

• Displaying STP Guard Configuration

Table 33-1. FTOS Supported Spanning Tree Protocols

Dell Force10 Term IEEE Specification

Spanning Tree Protocol (STP) 802.1d

Rapid Spanning Tree Protocol (RSTP) 802.1w

Multiple Spanning Tree Protocol (MSTP) 802.1s

Per-VLAN Spanning Tree Plus (PVST+) Third Party