Cisco Systems 3750E manual Configuring STP, Understanding Spanning-Tree Features, 18-1

C H A P T E R 18

Configuring STP

This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on the Catalyst 3750-E or 3560-E switch. The switch can use either the per-VLAN spanning-tree plus (PVST+) protocol based on the IEEE 802.1D standard and Cisco proprietary extensions, or the rapid per-VLAN spanning-tree plus (rapid-PVST+) protocol based on the IEEE 802.1w standard. A switch stack appears as a single spanning-tree node to the rest of the network, and all stack members use the same bridge ID. Unless otherwise noted, the term switch refers to a Catalyst 3750-E or 3560-E standalone switch and to a Catalyst 3750-E switch stack.

For information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs to the same spanning-tree instance, see Chapter 19, “Configuring MSTP.” For information about other spanning-tree features such as Port Fast, UplinkFast, root guard, and so forth, see Chapter 20, “Configuring Optional Spanning-Tree Features.”

Note For complete syntax and usage information for the commands used in this chapter, see the command reference for this release.

This chapter consists of these sections:

•Understanding Spanning-Tree Features, page 18-1

•Configuring Spanning-Tree Features, page 18-12

•Displaying the Spanning-Tree Status, page 18-24

Understanding Spanning-Tree Features

These sections contain this conceptual information:

•STP Overview, page 18-2

•Spanning-Tree Topology and BPDUs, page 18-3

•Bridge ID, Switch Priority, and Extended System ID, page 18-4

•Spanning-Tree Interface States, page 18-5

•How a Switch or Port Becomes the Root Switch or Root Port, page 18-8

•Spanning Tree and Redundant Connectivity, page 18-9

•Spanning-Tree Address Management, page 18-9

•Accelerated Aging to Retain Connectivity, page 18-9

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 18-1