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Regarding MSTP, is it possible to have different VLAN mapping for different regions ?

Example: Region 1: Instance 1: VLAN 10,20,30 Instance 2: VLAN 40,50,60

Region 2: Instance 1: VLAN 10,50,60 Instance 2: VLAN 20,30,40

Also I read in Cisco press CCNP references: "VLANs are grouped into an instance, and each instance elects a root bridge."

So you confirm that inside a region, we have one root bridge per instance ? So inside a region we could have different root bridge for different instances ?

So in conclusion inside a region composed of three bridge for example, A, B and C, A could be the root bridge for the IST (instance 0), B could be the root bridge for the instance 1 and C the root bridge for the instance 2 ?

Thanks.

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Regarding MSTP, is it possible to have different VLAN mapping for different regions ?

Example: Region 1: Instance 1: VLAN 10,20,30 Instance 2: VLAN 40,50,60

Region 2: Instance 1: VLAN 10,50,60 Instance 2: VLAN 20,30,40

Yes, see catalyst 3560 config guide:

The MSTP enables multiple VLANs to be mapped to the same spanning-tree instance, reducing the number of spanning-tree instances needed to support a large number of VLANs.

Regarding:

So you confirm that inside a region, we have one root bridge per instance ? So inside a region we could have different root bridge for different instances ?

So in conclusion inside a region composed of three bridge for example, A, B and C, A could be the root bridge for the IST (instance 0), B could be the root bridge for the instance 1 and C the root bridge for the instance 2 ?

Correct, each MST instance has its own topology parameters.

I know you tagged Cisco, but if someone from Juniper also needs to check for their wording: Understanding MSTP for EX Series and QFX Series Switches

An MSTP region can support up to 64 MSTIs,, and each MSTI can support from 1 to 4094 VLANs. When you define a region, MSTP automatically creates an internal spanning-tree instance (IST instance 0) that provides the root switch for the region and includes all currently configured VLANs that are not specifically assigned to a user-defined MSTI.

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You group VLAN IDs into instances which each form their own spanning tree with its own root bridge. Using different instances has the advantage that some instances/groups can use links that others won't. This way, you can make use of redundant links that would be useless with a single instance.

A region is a part of the network that your instances are confined in. Spanning trees don't span across region boundaries. So, each region can do what it wants without impacting any other.

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