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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
78-17058-01
Chapter15 Configuring MSTP Configuring MSTP Features
Configuring Port Priority
If a loop occurs, the MSTP uses the port priority when selecting an NNI to put into the forwarding state.
You can assign higher priority values (lower numerical values) to NNIs that you want selected first and
lower priority values (higher numerical values) that you want selected last. If all interfaces ha ve the sa me
priority value, the MSTP puts the interface with the lowest interfa ce n umber in the f o rw a rdin g 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.
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.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Specify an interface to configure, and enter interface
configuration mode.
Valid interfaces include physical NNIs and NNI port
channels. The port-channel range is 1 to 48.
Note If a physical interface is not an NNI, enter the
port-type nni interface configuration command
before attempting to configure MST port priority.
If the interface is a port channel, all members of the
port channel must be NNIs.
Step3 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 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.
Step4 end Return to privileged EXEC mode.
Step5 show spanning-tree mst interface interface-id
or
show spanning-tree mst instance-id
Verify your entries.
Step6 copy running-config startup-config (Optional) Save your entries in the configuration file.