Cisco Systems 3750E manual Monitoring and Maintaining Fallback Bridging, Clear bridge bridge-group

Chapter 44 Configuring Fallback Bridging

Monitoring and Maintaining Fallback Bridging

Disabling the Spanning Tree on an Interface

When a loop-free path exists between any two switched subnetworks, you can prevent BPDUs generated in one switching subnetwork from impacting devices in the other switching subnetwork, yet still permit switching throughout the network as a whole. For example, when switched LAN subnetworks are separated by a WAN, BPDUs can be prevented from traveling across the WAN link.

Beginning in privileged EXEC mode, follow these steps to disable spanning tree on a port. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify the port, and enter interface configuration mode.
Step 3
	bridge-group bridge-group	Disable spanning tree on the port.
	spanning-disabled	For bridge-group, specify the bridge group number. The range is 1
		to 255.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show running-config	Verify your entry.
Step 6
	copy running-config startup-config	(Optional) Save your entry in the configuration file.

To re-enable spanning tree on the port, use the no bridge-groupbridge-groupspanning-disabledinterface configuration command.

This example shows how to disable spanning tree on a port in bridge group 10:

Switch(config)# interface gigabitethernet2/0/1

Switch(config-if)#bridge group 10 spanning-disabled

Monitoring and Maintaining Fallback Bridging

To monitor and maintain the network, use one or more of the privileged EXEC commands in Table 44-2:

Table 44-2 Commands for Monitoring and Maintaining Fallback Bridging

Command	Purpose
clear bridge bridge-group	Removes any learned entries from the forwarding
	database.
show bridge [bridge-group]group	Displays details about the bridge group.
show bridge [bridge-group][interface-id	Displays MAC addresses learned in the bridge group.
mac-address verbose]

To display the bridge-group MAC address table on a stack member, start a session from the stack master to the stack member by using the session stack-member-numberglobal configuration command. Enter the show bridge [bridge-group] [interface-id mac-address verbose] privileged EXEC command at the stack member prompt.

For information about the fields in these displays, see the Cisco IOS Bridging and IBM Networking Command Reference, Volume 1 of 2, Release 12.2.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		44-11