IBM 12.1(22)EA6 User Manual

11-16

Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide

24R9746

Chapter 11 Configuring Optional Spanning-Tree Features

Configuring Optional Spanning-Tree Features

To disable root guard, use the no spanning-tree guard interface configuration command.

Enabling Loop Guard

You can use loop guard to prevent alternate or root ports from becoming designated ports because of a
failure that leads to a unidirectional link. This feature is most effective when it is configured on the entire
switched network. Loop guard operates only on ports that are considered point-to-point by the spanning
tree.

Note

You cannot enable both loop guard and root guard at the same time.

You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.

Beginning in privileged EXEC mode, follow these steps to enable loop guard. This procedure is optional.

To globally disable loop guard, use the no spanning-tree loopguard default global configuration
command. You can override the setting of the no spanning-tree loopguard default global configuration
command by using the spanning-tree guard loop interface configuration command.

Step 4

end

Return to privileged EXEC mode.

Step 5

show running-config

Verify your entries.

Step 6

copy running-config startup-config (Optional) Save your entries in the configuration file.

Command

Purpose

Command

Purpose

Step 1

show spanning-tree active

show spanning-tree mst

Determine which ports are alternate or root ports.

Step 2

configure terminal

Enter global configuration mode.

Step 3

spanning-tree loopguard default

Enable loop guard.

By default, loop guard is disabled.