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Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 46 Configuring Fallback Bridging
Configuring Fallback Bridging
Changing the Maximum-Idle Interval
If a switch does not receive BPDUs from the root switch within a specified interval, it recomputes the
spanning-tree topology.
Beginning in privileged EXEC mode, follow these steps to change the maximum-idle interval (maximum
aging time). This procedure is optional.
To return to the default setting, use the no bridge bridge-group max-age global configuration command.
This example shows how to change the maximum-idle interval to 30 seconds in bridge group 10:
Switch(config)# bridge 10 max-age 30
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.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
bridge bridge-group max-age seconds Specify the interval that the switch waits to hear BPDUs from the root
switch.
• For bridge-group, specify the bridge group number. The range is 1
to
255.
• For seconds, enter a number from 6 to 200. The default is 30.
Step 3
end Return to privileged EXEC mode.
Step 4
show running-config Verify your entry.
Step 5
copy running-config startup-config (Optional) Save your entry in the configuration file.
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.