Configuring Port Priority - Cisco Catalyst 3750-X Software Configuration Manual

Configuring MSTP Features
Beginning in privileged EXEC mode, follow these steps to configure a switch as the secondary root
switch. This procedure is optional.
Command
Step 1
configure terminal
Step 2
spanning-tree mst instance-id root
secondary [diameter net-diameter
[hello-time seconds]]
Step 3
end
Step 4
show spanning-tree mst instance-id
Step 5 copy running-config startup-config
To return the switch to its default setting, use the no spanning-tree mst instance-id root global
configuration command.

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.
If your Catalyst 3750-X switch is a member of a switch stack, you must use the spanning-tree mst
Note
[instance-id] cost cost interface configuration command instead of the spanning-tree mst [instance-id]
port-priority priority interface configuration command to select a port to put in the forwarding state.
Assign lower cost values to ports that you want selected first and higher cost values to ports that you
want selected last. For more information, see the
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
21-20
Purpose
Enter global configuration mode.
Configure a switch as the secondary root switch.
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.
(Optional) For diameter net-diameter, specify the maximum
•
number of switches between any two end stations. The range is 2
to 7. This keyword is available only for MST instance 0.
(Optional) For hello-time seconds, specify the interval in
•
seconds between the generation of configuration messages by
the root switch. The range is 1 to 10 seconds; the default
is 2 seconds.
Use the same network diameter and hello-time values that you used
when configuring the primary root switch. See the
Root Switch" section on page
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
"Configuring Path Cost" section on page
Chapter 21 Configuring MSTP
"Configuring the
21-18.
21-21.
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