Cisco Systems 3750E manual Spanning-tree mst instance-id cost cost, 19-21

Chapter 19 Configuring MSTP

Configuring MSTP Features

To return the interface to its default setting, use the no spanning-tree mst instance-idport-priorityinterface configuration command.

Configuring Path Cost

The MSTP path cost default value is derived from the media speed of an interface. If a loop occurs, the MSTP uses cost when selecting an interface to put in the forwarding state. You can assign lower cost values to interfaces that you want selected first and higher cost values that you want selected last. If all interfaces have the same cost value, the MSTP puts the interface with the lowest interface number in the forwarding state and blocks the other interfaces.

Beginning in privileged EXEC mode, follow these steps to configure the MSTP cost of an interface. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify an interface to configure, and enter interface
		configuration mode. Valid interfaces include physical ports and
		port-channel logical interfaces. The port-channel range is 1 to 48.
Step 3
	spanning-tree mst instance-idcost cost	Configure the cost.
		If a loop occurs, the MSTP uses the path cost when selecting an
		interface to place into the forwarding state. A lower path cost
		represents higher-speed transmission.
		• For instance-id, you can specify a single instance, a range of
		instances separated by a hyphen, or a series of instances
		separated by a comma. The range is 0 to 4094.
		• For cost, the range is 1 to 200000000; the default value is
		derived from the media speed of the interface.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show spanning-tree mst interface interface-id	Verify your entries.
	or
	show spanning-tree mst instance-id
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

Note The show spanning-tree mst interface interface-idprivileged EXEC command displays information only for ports that are in a link-up operative state. Otherwise, you can use the show running-configprivileged EXEC command to confirm the configuration.

To return the interface to its default setting, use the no spanning-tree mst instance-idcost interface configuration command.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		19-21