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MSTP vlan addition

Mallanna
Occasional Visitor

MSTP vlan addition

Hi,

I have new switch and need to have new vlans on it, routing will happen through core switch, i have one mstp region with multiple vlans and 2 instance are running, if i create only new vlans on new switch and map it to existing instance will mstp region will change? do i need to create existing vlans and new vlans on all switches even it is not required.
4 REPLIES
Jeff Carrell
Honored Contributor

Re: MSTP vlan addition

When MSTP is enabled, all vlans (1-4094) are preassigned to the IST (internal instance), so as you "create" a vlan, it already has a spanning-tree instance home.

As you create vlans, there is no change to the MSTP config.

If you subsequently configure a vlan to a specific MSTP instance, then the MSTP config has changed, and then yes, all switches in that MSTP region must be configured _identically_ (create vlans, map to specific instance - even if those vlans are not used) or the switches will be in different MSTP domains, and MSTP will not work correctly.

hth...Jeff
Mallanna
Occasional Visitor

Re: MSTP vlan addition

Thanks, while changing mst instance will it be any fluctioation in the ntwork, because i am going to do changes in production environment, if yes i will have take approval for dowtime.
Jeff Carrell
Honored Contributor

Re: MSTP vlan addition

Mallanna asked: "while changing mst instance will it be any fluctuation in the network, because i am going to do changes in production environment, if yes i will have take approval for downtime."

There is always a chance some disruption could occur.

I would schedule an outage and make changes. (best practice when possible anyway)

Since changes should be the same, you could commands in a text editor, then copy and paste them into the switch config, at least it speeds up the process some.

hth...Jeff
Mallanna
Occasional Visitor

Re: MSTP vlan addition


Thank you very much Jeff...