CHAPT ER
18-1
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
18
Configuring STP
This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on the
Catalyst 3750 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 standalone switch and to a 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 Chapter20,
“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, page18-1
Configuring Spanning-Tree Features, page18-12
Displaying the Spanning-Tree Status, page18-24

Understanding Spanning-Tree Features

These sections contain this conceptual information:
STP Overview, page18-2
Spanning-Tree Topology and BPDUs, page18-3
Bridge ID, Switch Priority, and Extended System ID, page18-5
Spanning-Tree Interface States, page18-5
How a Switch or Port Becomes the Root Switch or Root Port, page18-8
Spanning Tree and Redundant Connectivity, page18-9
Spanning-Tree Address Management, page18-9
Accelerated Aging to Retain Connectivity, page18-9
Spanning-Tree Modes and Protocols, page18-10