MST spanning-tree

[loc.nguyen]

Hi,

I tried to understand a spanning tree setting on an old switch so that I can move it to a new switch.

 The configuration on the old switch is as below:

spanning-tree mode mst
spanning-tree extend system-id
!
spanning-tree mst configuration
name BACKBONE
revision 1
!

spanning-tree mst 0-1,8 priority 4096

spanning-tree vlan 11,101-102,104,106 priority 4096

The switch doesn't have trunk set up with anything and the only vlan on switch is vlan 11;

I think can replace all the config above with: 

spanning-tree vlan 11 priority 4096

Can you advise?

Thanks

Loc

[Reza Sharifi · Accepted solution]

Hi,

If you only have one vlan then the command:

 spanning-tree vlan 11 priority 4096

Should be sufficient to change the priority.

HTH 

[MHM Cisco World]

Friend we talk about MST not PVST so each vlan's have one priority if it in same instance' you can not config different priority for each vlan in mst.

So retrun to your config you config revision but no instance so by defualt all vlan in instance 0 and this instance ypu config it priority by 

spanning-tree mst 0-1,8 priority 4096

So instance 0 that have all vlan have priority 4096.

MHM

[David Ruess]

Hello,

As the switch is configured to use MST you would need to change the priority of the MST instance (0 by default for all VLANs if nothing is configured)

spanning-tree mst 0 priority 4096

If you just want to change VLANs 11 priority you will need to convert the Spanning tree mode to rapid-pvst and then change it with the command you mention of:

spanning-tree vlan 11 priority 4096

-David

[MHM Cisco World]

You migrate config from old to new SW 

Old use mst for reason dont change the stp mode.

MHM