Cisco Catalyst 4500 Series, Software Configuration Manual

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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 26 Configuring Optional STP Features
Enabling Loop Guard
Enabling Loop Guard
You can enable loop guard globally or per-port.
Loop Guard can be enabled only on network and normal spanning tree port types.
To enable loop guard globally on the switch, perform this task:
This example shows how to enable loop guard globally:
Switch(config)# spanning-tree loopguard default
Switch(config)# Ctrl-Z
This example shows how to verify the previous configuration of port 4/4:
Switch# show spanning-tree interface fastethernet 4/4 detail
Port 196 (FastEthernet4/4) of VLAN0010 is forwarding
Port path cost 1000, Port priority 160, Port Identifier 160.196.
Designated root has priority 32768, address 00d0.00b8.140a
Designated bridge has priority 32768, address 00d0.00b8.140a
Designated port id is 160.196, designated path cost 0
Timers:message age 0, forward delay 0, hold 0
Number of transitions to forwarding state:1
The port is in the portfast mode by portfast trunk configuration
Link type is point-to-point by default
Bpdu filter is enabled
Loop guard is enabled by default on the port
BPDU:sent 0, received 0
To enable loop guard on an interface, perform this task:
This example shows how to enable loop guard on port 4/4:
Switch(config)# interface fastEthernet 4/4
Switch(config-if)# spanning-tree guard loop
Switch(config-if)# ^Z
Command Purpose
Step 1
Switch(config)# spanning-tree loopguard default
Enables loop guard globally on the switch.
Step 2
Switch(config)# end Exits configuration mode.
Step 3
Switch# show spanning tree interface 4/4 detail
Verifies the configuration impact on a port.
Command Purpose
Step 1
Switch(config)# interface { type slot/port } |
{ port-channel port_channel_number }
Selects an interface to configure.
Step 2
Switch(config-if)# spanning-tree guard loop
Configures loop guard.
Step 3
Switch(config)# end
Exits configuration mode.
Step 4
Switch# show spanning tree interface 4/4 detail
Verifies the configuration impact on that port.