Configuring basic MSTP parameters

Follow these steps to configure basic MSTP parameters.

Procedure

  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

    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