Changing MSTP Port Parameters

The path cost for a port comes from the speed of that port if there is no path cost configuration.
If you do not want the link speed to influence the path cost and affect the network topology, then configure the path cost for the port. You can configure a single port, multiple port, or a port range.
  1. Enter the following command in global configuration mode level to configure a system into MSTP mode. 
    device(config)# mstp scope all
  2. Enter a command such as the following to configure the path cost configuration and the priority together. 
    device(config)# mstp instance 0 ethernet 1/1/4 ethernet 1/1/5 ethernet 1/1/15 to 1/1/17 path-cost 20000 priority 192
    You can configure path cost and priority separately.
  3. Enter the following command to enable MSTP in global configuration mode level. 
    device(config)# mstp start
  4. Verify the running configuration. 
    device(config)# show run | include mstp
    mstp scope all
mstp instance 0 vlan 1
mstp instance 0 ethe 1/1/4 to 1/1/5 ethe 1/1/15 to 1/1/17 path-cost 20000
mstp instance 0 ethe 1/1/4 to 1/1/5 ethe 1/1/15 to 1/1/17 priority 64
mstp start
Parent topic: 802.1s Multiple Spanning Tree Protocol