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Catalyst 3560 Switch Software Configuration Guide
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Chapter 34 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.
To re-enable spanning tree on the port, use the no bridge-group bridge-group spanning-disabled
interface configuration command.
This example shows how to disable spanning tree on a port in bridge group 10:
Switch(config)# interface gigabitethernet0/1
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 34-2
:
For information about the fields in these displays, refer to the Cisco IOS Bridging and IBM Networking
Command Reference for Release 12.1.
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
spanning-disabled
Disable spanning tree on the port.
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.
Table 34-2 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 |
mac-address | verbose]
Displays MAC addresses learned in the bridge group.
