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Catalyst 3750 Switch Command Reference
OL-8552-07
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
spanning-tree mst port-priority
spanning-tree mst port-priority
Use the spanning-tree mst port-priority interface configuration command to configure an interface
priority. If a loop occurs, the Multiple Spanning Tree Protocol (MSTP) can find the interface to put in
the forwarding state. Use the no form of this command to return to the default setting.
spanning-tree mst instance-id port-priority priority
no spanning-tree mst instance-id port-priority
Syntax Description
Defaults The default is 128.
Command Modes Interface configuration
Command History
Usage Guidelines You can assign higher priority values (lower numerical values) to interfaces that you want selected first
and lower priority values (higher numerical values) that you want selected last. If all interfaces have the
same priority value, the multiple spanning tree (MST) puts the interface with the lowest interface
number in the forwarding state and blocks other interfaces.
If your switch is a member of a switch stack, you must use the spanning-tree mst [instance-id] cost cost
interface configuration command instead of the spanning-tree mst [instance vlan-id] port-priority
priority interface configuration command to select an interface to put in the forwarding state. Assign
lower cost values to interfaces that you want selected first and higher cost values to interfaces that you
want selected last.
Examples This example shows how to increase the likelihood that the interface associated with spanning-tree
instances 20 and 22 is placed into the forwarding state if a loop occurs:
Switch(config)# interface gigabitethernet2/0/2
Switch(config-if)# spanning-tree mst 20,22 port-priority 0
You can verify your settings by entering the show spanning-tree mst interface interface-id privileged
EXEC command.
instance-id Range of spanning-tree instances. 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.
priority The range is 0 to 240 in increments of 16. Valid priority values are 0, 16, 32, 48, 64,
80, 96, 112, 128, 144, 160, 176, 192, 208, 224, and 240. All other values are
rejected. The lower the number, the higher the priority.
Release Modification
12.1(14)EA1 This command was introduced.
12.2(25)SEC The instance-id range changed to 1 to 4094.
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