Configuring basic MSTP parameters

Follow these steps to configure basic MSTP parameters.

1. Enter global configuration mode.
   

   device# configure terminal
   

2. Enable MSTP.
   

   device(config)# protocol spanning-tree mstp
   

3. Specify the region name.
   

   device(config-mstp)# region connemara
   

4. Specify the revision number.
   

   device(config-mstp)# revision 1
   

5. Map MSTP instances to VLANs.
   1. Map instance 1 to VLANs 2 and 3.
      

      device(config-mstp)# instance 1 vlan 2,3
      

   2. Map instance 2 to VLANs 4, 5, and 6.
      

      device(config-mstp)# instance 2 vlan 4-6
      

6. Set a priority for an instance.
   

   device(conf-Mstp)# instance 1 priority 28672
   

   The priority ranges from 0 through 61440 and the value must be in multiples of 4096.
7. Specify the maximum hops for a BPDU.
   

   device(conf-Mstp)# max-hops 25
   

   This prevents the messages from looping indefinitely on an interface
8. Return to privileged EXEC mode.
   

   device(conf-Mstp)# end
   

9. Verify the configuration.
   

   device# show spanning-tree mst
   
    Spanning-tree Mode: Multiple Spanning Tree Protocol
   
    CIST Root Id: 8000.609c.9f5d.4800 (self)
    CIST Bridge Id: 8000.609c.9f5d.4800
    CIST Reg Root Id: 8000.609c.9f5d.4800 (self)
   
    CIST Root Forward Delay: 15; Hello Time: 2; Max Age: 20; Max-hops: 20
    Configured Forward Delay: 15; Hello Time: 2; Max Age: 20; Max-hops: 25;
    Tx-HoldCount: 6
    Number of topology change(s): 0
   
    Bpdu-guard errdisable timeout: disabled
    Bpdu-guard errdisable timeout interval: 300 sec
    Migrate Time: 3 sec
   
     Name           : connemara
     Revision Level : 1
     Digest         : 0xD5FF4C3F6C18E2F27AF3A8300297ABAA
   
     Instance        VLAN
     --------        ----
      0:             1,7,8,9
      1:             2,3
      2:             4-6
   

   

   Note

   Observe that the settings comply with the formula set out in the STP parameters section, as:

   (2 × (forward delay - 1)) ≥ maximum age ≥ (2 × (hello time + 1))

   or in this case: 28 ≥ 20 ≥ 6.

   

   device# show running-config | begin spanning-tree
   protocol spanning-tree mstp
    instance 1 vlan 2,3
    instance 1 priority 28672
    instance 2 vlan 4-6
    region connemars
    revision 1
    max-hops 25
    !
   ... 
   

10. Save the configuration
    

    device# copy running-config startup-config
    

Basic MSTP configuration example

device# configure terminal
device(config)# protocol spanning-tree mstp
device(config-mstp)# region connemara
device(config-mstp)# revision 1
device(config-mstp)# instance 1 vlan 2,3
device(config-mstp)# instance 2 vlan 4-6
device(conf-Mstp)# instance 1 priority 28582
device(conf-Mstp)# max-hops 25
device(conf-Mstp)# end
device# show spanning-tree mst
device# copy running-config startup-config