802.1s Multiple Spanning Tree

MSTP (IEEE 802.1s) is an IEEE standard that allows several VLANs to be mapped to a reduced number of spanning-tree instances. This provides advantages over PVST+ because typical topologies need only a few spanning-tree topologies to be optimized.
We configure a set of switches with the same MISTP parameters, and this becomes an MST region. With MISTP, you have an internal spanning tree capable of representing the entire MST region as a common spanning tree for backward compatibility with earlier IEEE implementations.

Follow are the steps to configure MISTP:

Step 1. Globally enable MISTP (MSTP) on your switches:

spanning-tree mode mst

Step 2. Enter MST configuration submode:

spanning-tree mst configuration

Step 3. Set the MST region name:

name name

Step 4. Set a configuration revision number:

revision rev_num

Step 5. Map your VLANs to MST instances:

instance int vlan range


We can verify an MSTP configuration using the following commands:

show spanning-tree mst configuration
show spanning-tree mst vlan_id