Configuring Port Priority - Cisco Catalyst 3750 Software Configuration Manual

Chapter 15 Configuring MSTP

Configuring Port Priority

If a loop occurs, the MSTP uses the port priority when selecting an interface to put into the forwarding
state. 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 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 port priority of an
interface. This procedure is optional.
Command
Step 1
configure terminal
Step 2 interface interface-id
Step 3 spanning-tree mst instance-id port-priority priority
Step 4
end
Step 5 show spanning-tree mst interface interface-id
or
show spanning-tree mst instance-id
Step 6
copy running-config startup-config
The show spanning-tree mst interface interface-id privileged EXEC command displays information
Note
only if the port is in a link-up operative state. Otherwise, you can use the show running-config interface
privileged EXEC command to confirm the configuration.
To return the interface to its default setting, use the no spanning-tree mst instance-id port-priority
interface configuration command.
78-15870-01
Purpose
Enter global configuration mode.
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 12.
Configure the port priority.
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 15.
For priority, the range is 0 to 240 in increments of 16.
•
The default is 128. The lower the number, the higher
the priority.
The 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.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Catalyst 3750 Metro Switch Software Configuration Guide
Configuring MSTP Features
15-17