Configure MST Properties of an Interface

See STP Topology Example for the topology for this procedure. You must perform this procedure before creating MST instances and regions in all the switches.

1. Create MST instances and regions in all the switches.

   SEFOS# configure terminal
   SEFOS(config)# spanning-tree mst configuration

2. Map VLANs to an MST instance.

   SEFOS(config-mst)# instance 1 vlan 1 

3. Specify a configuration name for an MST region.

   SEFOS(config-mst)# name region1

   Instance range is 1-16 and VLAN range is 1-4096.

4. Return to Privileged EXEC mode.

   SEFOS(config-mst)# end

5. After the topology stabilizes, type this command in all the switches:
   1. In switch 1, type.

      SEFOS# show spanning-tree mst 1
       
      #MST01
      Vlans mapped:    1
      Bridge     Address 00:01:02:03:04:01    Priority 32768
      Root       Address 00:01:02:03:04:01    Priority 32768
      Root       this switch for MST01
      Interface Role        Sts       Cost  Prio.Nbr Type
      --------- ----         ---          ----     -------- ----
      Ex0/1  Designated  Forwarding  200000  128.1  Link Type is Shared
      Ex0/2  Designated  Forwarding  200000  128.2  Link Type is Shared
      Ex0/3  Designated  Forwarding  200000  128.3  Link Type is Shared

   2. In switch 2, type.

      SEFOS# show spanning-tree mst 1
       
      ## MST01
      Vlans mapped:    1
      Bridge     Address 00:02:02:03:04:01    Priority 32768
      Root       Address 00:01:02:03:04:01    Priority 32768
      Interface Role        Sts         Cost     Prio.Nbr Type
      --------- ----         ---          ----     -------- ----
      Ex0/1     Root        Forwarding  200000   128.1     Link Type is Shared
      Ex0/2     Designated  Forwarding  200000   128.2     Link Type is Shared

   3. In switch 3, type.

      SEFOS# show spanning-tree mst 1
      ## MST01
      Vlans mapped:    1
      Bridge     Address 00:03:02:03:04:01    Priority 32768
      Root       Address 00:01:02:03:04:01    Priority 32768
      Interface Role       Sts         Cost     Prio.Nbr  Type
      --------- ----         ---          ----     -------- ----
      Ex0/1     Root   Forwarding  200000   128.1    Link Type is Shared
      Ex0/2  Alternate Discarding  200000   128.2    Link Type is Shared
      Ex0/3  Alternate Discarding  200000  128.3     Link Type is Shared

6. In switch 1, specify the interface for which the port priority is to be configured.

   Interfaces can be physical interfaces and port-channel logical interfaces (port-channel port-channel-number).

   SEFOS# configure terminal
   SEFOS(config)# interface extreme-ethernet 0/3

7. In switch 1, configure the port priority for spanning tree.

   After you configure the port priority for port 3 in switch 1, port 1 and port 2 of switch 2 are alternate ports. Port 3 is the root port.

   SEFOS(config-if)# spanning-tree mst 1 port-priority 32
   SEFOS(config)# end

   For priority, the range is 0 to 240 in increments of 16. The default is 128. The lower the number, the higher the priority.

   Valid 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.

8. View the multiple spanning tree information for the CIST instance or specified MST instance.

   For instance id, the range is 1-64. detail displays spanning tree MST instance specific details.

   1. In switch 1, type.

      SEFOS# show spanning-tree mst 1
       
      #MST01
      Vlans mapped:    1
      Bridge     Address 00:01:02:03:04:01    Priority 32768
      Root       Address 00:01:02:03:04:01    Priority 32768
      Root       this switch for MST01
      Interface Role        Sts       Cost   Prio.Nbr   Type
      --------- ----         ---          ----     -------- ----
      Ex0/1   Designated  Forwarding 200000  128.1  Link Type is Shared
      Ex0/2   Designated  Forwarding 200000  128.2  Link Type is Shared
      Ex0/3   Designated  Forwarding 200000   32.3  Link Type is Shared

   2. In switch 2, type.

      SEFOS# show spanning-tree mst 1
       
      ## MST01
      Vlans mapped:    1
      Bridge     Address 00:02:02:03:04:01    Priority 32768
      Root       Address 00:01:02:03:04:01    Priority 32768
      Interface Role        Sts         Cost     Prio.Nbr Type
      --------- ----        ---         ----     -------- ----
      Ex0/1     Root        Forwarding  200000   128.1    Link Type is Shared
      Ex0/2     Designated  Forwarding  200000   128.2    Link Type is Shared

   3. In switch 3, type.

      SEFOS# show spanning-tree mst 1
       
      ## MST01
      Vlans mapped:    1
      Bridge     Address 00:03:02:03:04:01    Priority 32768
      Root       Address 00:01:02:03:04:01    Priority 32768
      Interface Role        Sts         Cost     Prio.Nbr Type
      --------- ----         ---        ----     -------- ----
      Ex0/1     Alternate   Discarding  200000   128.1    Link Type is Shared
      Ex0/2     Alternate   Discarding  200000   128.2    Link Type is Shared
      Ex0/3     Root        Forwarding  200000   128.3    Link Type is Shared