Chapter 18 Configuring STP

Configuring Spanning-Tree Features

Changing the Spanning-Tree Mode.

The switch supports three spanning-tree modes: PVST+, rapid PVST+, or MSTP. By default, the switch runs the PVST+ protocol.

Beginning in privileged EXEC mode, follow these steps to change the spanning-tree mode. If you want to enable a mode that is different from the default mode, this procedure is required.

 

Command

Purpose

Step 1

 

 

configure terminal

Enter global configuration mode.

 

 

 

Step 2 spanning-tree mode {pvst mst

Configure a spanning-tree mode. All stack members run the same

 

rapid-pvst}

version of spanning-tree.

 

 

Select pvst to enable PVST+ (the default setting).

 

 

Select mst to enable MSTP (and RSTP). For more configuration

 

 

steps, see Chapter 19, “Configuring MSTP.”

 

 

Select rapid-pvstto enable rapid PVST+.

Step 3

 

 

interface interface-id

(Recommended for rapid-PVST+ mode only) Specify an interface to

 

 

configure, and enter interface configuration mode. Valid interfaces

 

 

include physical ports, VLANs, and port channels. The VLAN ID range

 

 

is 1 to 4094. The port-channel range is 1 to 48.

Step 4

 

 

spanning-tree link-type point-to-point

(Recommended for rapid-PVST+ mode only) Specify that the link type

 

 

for this port is point-to-point.

 

 

If you connect this port (local port) to a remote port through a

 

 

point-to-point link and the local port becomes a designated port, the

 

 

switch negotiates with the remote port and rapidly changes the local

 

 

port to the forwarding state.

Step 5

 

 

end

Return to privileged EXEC mode.

Step 6

 

 

clear spanning-tree detected-protocols

(Recommended for rapid-PVST+ mode only) If any port on the switch

 

 

is connected to a port on a legacy IEEE 802.1D switch, restart the

 

 

protocol migration process on the entire switch.

 

 

This step is optional if the designated switch detects that this switch is

 

 

running rapid PVST+.

Step 7

 

 

show spanning-tree summary

Verify your entries.

 

and

 

 

show spanning-tree interface

 

 

interface-id

 

Step 8

 

 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

 

 

 

To return to the default setting, use the no spanning-tree mode global configuration command. To return the port to its default setting, use the no spanning-treelink-typeinterface configuration command.

 

 

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

 

 

 

 

 

 

OL-9775-02

 

 

18-15

 

 

 

 

 

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Cisco Systems 3750E manual Changing the Spanning-Tree Mode, 18-15