Specifications

CHAPTER

11-1

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

OL-26895-01

Configuring Optional Spanning-Tree Features

This chapter describes how to configure optional spanning-tree features on the Cisco MWR 2941router.

You can configure all of these features when your router is running per-VLAN spanning-tree plus

(PVST+). You can configure only the noted features when your router is running the Multiple Spanning

Tree Protocol (MSTP) protocol. 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 switch do not participate in STP. UNIs and ENIs on which

STP is not enabled immediately forward traffic when they are brought up.

For information on configuring the PVST+, see Chapter 9, “Configuring STP.” 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 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.

• Understanding Optional Spanning-Tree Features, page 11-1

• Configuring Optional Spanning-Tree Features, page 11-5

• Displaying the Spanning-Tree Status, page 11-10

Understanding Optional Spanning-Tree Features

• Understanding Port Fast, page 11-1

• Understanding BPDU Guard, page 11-2

• Understanding BPDU Filtering, page 11-3

• Understanding Root Guard, page 11-3

• Understanding Loop Guard, page 11-4

Understanding Port Fast

Port Fast immediately brings an STP port configured as an access or trunk port to the forwarding state

from a blocking state, bypassing the listening and learning states.

Note By default, STP is enabled on NNIs and disabled on ENIs. To configure an ENI as an STP port, enter

the spanning-tree interface configuration command to configure the port as an STP port.