Cisco Nexus 5000 Series Switch CLI Software Configuration Guide (OL-16597-01, July 2009)

Enabling Loop Guard or Root Guard on Specified Interfaces
You can enable either Loop Guard or Root Guard on specified interfaces.
Enabling Root Guard on a port means that port cannot become a root port, and LoopGuard prevents alternate
or root ports from becoming the designated port because of a failure that could lead to a unidirectional link.
Both Loop Guard and Root Guard enabled on an interface apply to all VLANs to which that interface belongs.
Entering the Loop Guard command for the specified interface overrides the global Loop Guard command.Note
Before You Begin
Ensure that STP is configured.
Ensure that you are configuring Loop Guard on spanning tree normal or network ports.
Procedure
PurposeCommand or Action
Enters configuration mode.switch# configure terminal
Step 1
Specifies the interface to configure, and enters the interface
configuration mode.
switch(config)# interface type
slot/port
Step 2
Enables or disables either Loop Guard or Root Guard for
the specified interface. By default, Root Guard is disabled
switch(config-if)# spanning-tree
guard {loop | root | none}
Step 3
by default, and Loop Guard on specified ports is also
disabled.
Loop Guard runs only on spanning tree normal
and network interfaces.
Note
This example shows how to enable Root Guard on Ethernet port 1/4:
switch# configure terminal
switch (config)# interface ethernet 1/4
switch(config-if)# spanning-tree guard root
Verifying STP Extension Configuration
To display the configuration information for the STP extensions, perform one of the following tasks:
PurposeCommand
Displays the current status of spanning tree on the
switch
switch# show running-config spanning-tree [all]
Displays selected detailed information for the current
spanning tree configuration.
switch# show spanning-tree [options]
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
210 OL-16597-01
About STP Extensions
Enabling Loop Guard or Root Guard on Specified Interfaces