Spanning-Tree Mst Port-Priority - Cisco Catalyst 3560-X Command Reference Manual

Chapter 2 Catalyst 3750-X and 3560-X Cisco IOS Commands

spanning-tree mst port-priority

Syntax Description
Defaults
Command Modes
Command History
Usage Guidelines
Examples
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Use the spanning-tree mst port-priority interface configuration command on the switch stack or on a
standalone switch 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
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.
The default is 128.
Interface configuration
Release
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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.
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.
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Modification
This command was introduced.
Catalyst 3750-X and 3560-X Switch Command Reference
spanning-tree mst port-priority
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