Configuring The Mst Port Cost - Cisco Nexus 7000 Series Configuration Manual

Configuring the MST Port Cost

Configuring the MST Port Cost
The MST port cost default value is derived from the media speed of an interface. If a loop occurs, MST uses
the 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 to interfaces values that you want selected last. If all interfaces
have the same cost value, MST puts the interface with the lowest interface number in the forwarding state
and blocks the other interfaces.
Note MST uses the long path-cost calculation method.
Before You Begin
Ensure that you are in the correct VDC (or enter the switchto vdc command).
SUMMARY STEPS
1. config t
2. interface {{type slot/port} | {port-channel number}}
3. spanning-tree mst instance-id cost {cost | auto}
4. exit
5. (Optional) show spanning-tree mst
6. (Optional) copy running-config startup-config
DETAILED STEPS
Command or Action
Step 1
config t
Example:
switch# config t
switch(config)#
Step 2 interface {{type slot/port} | {port-channel
number}}
Example:
switch# config t
switch(config)# interface ethernet 3/1
switch(config-if)#
Step 3
spanning-tree mst instance-id cost {cost | auto}
Example:
switch(config-if)# spanning-tree mst 4 cost
17031970
Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x
162
Purpose
Enters global configuration mode.
Specifies an interface to configure, and enters interface
configuration mode.
Configures the cost.
If a loop occurs, MST uses the path cost when selecting an
interface to place into the forwarding state. A lower path cost
represents higher-speed transmission as follows:
• 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 from 1 to 4094.
Configuring MST Using Cisco NX-OS