Hi! I have these scenario below:
instance 1 active
instance 2 standby
instance 1 standby
instance 2 active
What will be the effect in instance 0? How should r1 and r2 be configured? If I add new vlans in instance 2 (say vlan 30-35), what configuration should I do in instance 1 (if there is any)?
As I mentioned before, the addition of the vlans will not change the topology in the instances. The ports R1 and R2 will still remain the root posts for those instances as long as you donot change any parameters like priority/ cost/ port priority etc for those instances.
(pls rate helpful posts)
All the active vlans which have not explicitly been assigned to a particular instance will be a part of instance 0. there is no need to configure anything specific on instance 0 unless you want to engineer the traffic to take a specific path. The default values of that instance will be used to decide on the root bridge and the designated/root/blocked ports.
When you add more vlans to 1 instance, there is no config cchange that you have to do on other instances ( or even in the same instance as a matter of fact).
In brief : on each switch, every MSTP instance has some default valies for parameters like bridge-priority, port cost, port priority etc. The topology is formed according to these values. You can change these values for a particular instance so that a single port is blocking for that instance but forwarding for other..... or a bridge is root for 1 instance and non-root for other.
When you add vlans to the instance, there is no change in the topology or other instances. The traffic for those vlans will follow the liks that are in fwd state according to that instance.
Hope this is helpful. Please rate if it is.