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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring MSTP
Configuring MSTP Features
Beginning in privileged EXEC mode, follow these steps to configure the MSTP port priority of an
interface. This procedure is optional.
Note The show spanning-tree mst interface interface-id privileged EXEC command displays information
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.
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.
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-id port-priority priority 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
4094.
• 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.
Step 4
end Return to privileged EXEC mode.
Step 5
show spanning-tree mst interface interface-id
or
show spanning-tree mst instance-id
Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
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