I have a quick question regarding MSTP:

Do all the switches in an MSTP domain should agree to which VLANs are mapped to an instance?

Being that dumb, I've just caused an outage by just simply creating a VLAN and adding it to an instance on one of the two core switches. Can you explain what happened when I did that, just want to understand that? Did I have to first add it as a tagged VLAN on the trunk between the core switches?

What is the correct procedure to add a VLAN to MSTP domain?

What I did that caused the trouble:

Switch(config)# vlan 700
Switch(vlan-700)# name test
Switch(config)# spanning-tree instance 1 vlan 700

Switches: HP ProCurve 3500yl

1 Answer 1


The switches in a MSTP domain do agree which VLANs are mapped to which instances. Altering the mapping will change the configuration digest. The result of that will be two separate, degenerate MSTP domains. Any configuration applied to the internal spanning tree will become moot.

They way you are supposed to do it is to create a 'pending' configuration on all the switches first, then apply it simultaneously. See the section "Enabling an Entire MST Region at Once or Exchanging One Region Configuration for Another" in the Advanced Traffic Management Guide for details.

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