Add VLAN into MST without any impact

[ShahIrwan9489]

For example my existing  instance 1 (vlan 1-10). So I plan to create new VLAN 11. So can I create new instance instead add new vlan into instance 1. For example: 
- Instance 1(vlan 1-10),

- Instance 2 (Vlan 11-new vlan)..

So I apply instance 2 to core switch and all access switches. So it will impact recalculate at all my switches or not? 

Thanks

[Deepak Kumar]

Hi,

It will no recalculation for Instance 1 but there will be for Instance 2. Make sure that first, you have to setup Instance 2 root device.

[Giuseppe Larosa]

Hello @ShahIrwan9489 ,

there is impact in creating a new MST instance because in doing it you change the Vlans to instances mapping and during the change you create a multi region MST topology.

So you need to do this during a maintenance window.

In MST you can configure Vlans to MST instances mapping even before a specific VLAN exist in the VLAN database.

You can take advantage of this with a proper planning.

So the suggestion is to partititon the VLAN space 1 to 4094 in subsets to be associated to MST instances and to implement this change.

Later to have an impactless change you just need to create a VLAN that falls in a specific subset that is associated to a specific instance.

In other words when you add a new MST instance it is wise to associate a set of VLANS to it and not only a single VLAN.

Hope to help

Giuseppe