Cisco Catalyst 4500 series Administration Manual page 705

Chapter 25 Configuring Optional STP Features
Command
Step 2
Switch(config)# end
Step 3
Switch# show spanning tree interface 4/4 detail
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:
Command
Step 1
Switch(config)# interface {type slot/port} |
{port-channel port_channel_number}
Step 2
Switch(config-if)# spanning-tree guard loop
Step 3
Switch(config)# end
Step 4
Switch# show spanning tree interface 4/4 detail
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
This example shows how to verify the configuration impact on 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 on the port
BPDU:sent 0, received 0
Switch#
OL_28731-01
Purpose
Exits configuration mode.
Verifies the configuration impact on a port.
Purpose
Selects an interface to configure.
Configures loop guard.
Exits configuration mode.
Verifies the configuration impact on that port.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
Enabling Loop Guard
25-5