Specifications

CHAPTER

9-1

Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR

OL-26895-01

Configuring STP

This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on the

Cisco MWR 2941 router. The router can use 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. On the Cisco MWR 2941 router, STP

is enabled by default on network node interfaces (NNIs). It is disabled by default, but can be enabled,

on enhanced network interfaces (ENIs). User network interfaces (UNIs) on the router do not participate

in STP. UNIs and ENIs on which STP is not enabled immediately forward traffic when they are brought

up.

For information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs

to the same spanning-tree instance, see Chapter 10, “Configuring MSTP.” For information about other

spanning-tree features including Port Fast and root guard, see Chapter 11, “Configuring Optional

Spanning-Tree Features.”

For detailed information about the commands used in this chapter, see the Cisco MWR 2941 Mobile

Wireless Edge Router IOS Command Reference, Release 15.0(1)MR.

This chapter consists of these sections:

• Understanding Spanning-Tree Features, page 9-1

• Configuring Spanning-Tree Features, page 9-10

• Displaying the Spanning-Tree Status, page 9-22

Understanding Spanning-Tree Features

• STP Overview, page 9-2

• Spanning-Tree Topology and BPDUs, page 9-2

• Bridge ID, Switch Priority, and Extended System ID, page 9-3

• Spanning-Tree Interface States, page 9-4

• How a Switch or Port Becomes the Root Switch or Root Port, page 9-7

• Spanning Tree and Redundant Connectivity, page 9-7

• Spanning-Tree Address Management, page 9-8

• Accelerated Aging to Retain Connectivity, page 9-8

• Spanning-Tree Modes and Protocols, page 9-9

• Supported Spanning-Tree Instances, page 9-10