Cisco Systems 3750E manual Changing the VLAN-Bridge Spanning-Tree Priority, 44-7

Chapter 44 Configuring Fallback Bridging

Configuring Fallback Bridging

Changing the VLAN-Bridge Spanning-Tree Priority

You can globally configure the VLAN-bridge spanning-tree priority of a switch when it ties with another switch for the position as the root switch. You also can configure the likelihood that the switch will be selected as the root switch.

Beginning in privileged EXEC mode, follow these steps to change the switch priority. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	bridge bridge-group priority number	Change the VLAN-bridge spanning-tree priority of the switch.
		• For bridge-group, specify the bridge group number. The range is 1
		to 255.
		• For number, enter a number from 0 to 65535. The default is 32768.
		The lower the number, the more likely the switch will be chosen as
		the root.
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.

To return to the default setting, use the no bridge bridge-grouppriority global configuration command. To change the priority on a port, use the bridge-group priority interface configuration command (described in the next section).

This example shows how to set the switch priority to 100 for bridge group 10:

Switch(config)# bridge 10 priority 100

Changing the Interface Priority

You can change the priority for a port. When two switches tie for position as the root switch, you configure a port priority to break the tie. The switch with the lowest interface value is elected.

Beginning in privileged EXEC mode, follow these steps to change the interface priority. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify the interface to set the priority, and enter interface
		configuration mode.
Step 3
	bridge-group bridge-grouppriority	Change the priority of a port.
	number	• For bridge-group, specify the bridge group number. The range is 1
		to 255.
		• For number, enter a number from 0 to 255 in increments of 4. The
		lower the number, the more likely that the port on the switch will
		be chosen as the root. The default is 128.
Step 4
	end	Return to privileged EXEC mode.
		Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02			44-7