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ngthen
Beginner

Setting a root bridge when using MST

I am running MST on my network with 1 instance right now but will soon be 2.  If I issue the show spanning-tree command here is what I see:

MIB-SW-CORE-01#show spanning-tree

MST0
  Spanning tree enabled protocol mstp
  Root ID    Priority    32768
             Address     000d.2908.3b80
             Cost        0
             Port        3 (GigabitEthernet0/3)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768  (priority 32768 sys-id-ext 0)
             Address     000f.23c1.d100
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1               Desg FWD 20000     128.1    P2p
Gi0/2               Desg FWD 20000     128.2    P2p
Gi0/3               Root FWD 20000     128.3    P2p Pre-STD-Rx
Gi0/4               Desg FWD 20000     128.4    P2p
Gi0/11              Desg FWD 200000    128.11   P2p Edge
Gi0/12              Desg FWD 200000    128.12   P2p Edge


MST1
  Spanning tree enabled protocol mstp
  Root ID    Priority    32769
             Address     000d.2908.3b80
             Cost        20000
             Port        3 (GigabitEthernet0/3)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
             Address     000f.23c1.d100
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1               Desg FWD 20000     128.1    P2p
Gi0/2               Desg FWD 20000     128.2    P2p
Gi0/3               Root FWD 20000     128.3    P2p Pre-STD-Rx
Gi0/4               Desg FWD 20000     128.4    P2p
Gi0/11              Desg FWD 200000    128.11   P2p Edge
Gi0/12              Desg FWD 200000    128.12   P2p Edge

Is there a reason that my CORE switch is not showing up as the root even through I have the following?


spanning-tree mode mst
spanning-tree logging
spanning-tree portfast bpduguard default
spanning-tree extend system-id
!
spanning-tree mst configuration
name mib-mstp
revision 1
instance 1 vlan 1, 8, 13-14, 17, 151-152
!
spanning-tree vlan 1,8,13-14,17,151-152 priority 8192

1 ACCEPTED SOLUTION

Accepted Solutions
cadet alain
Advisor

Hi,

spanning-tree vlan 1,8,13-14,17,151-152 priority 8192

This is not for MST.

The correct syntax is span mst 1 priority 8192

Regards.

Alain.

Don't forget to rate helpful posts.

View solution in original post

1 REPLY 1
cadet alain
Advisor

Hi,

spanning-tree vlan 1,8,13-14,17,151-152 priority 8192

This is not for MST.

The correct syntax is span mst 1 priority 8192

Regards.

Alain.

Don't forget to rate helpful posts.

View solution in original post