notes: MSTP 802.1s

Multiple Spanning Tree
- MSTP is using RSTP
- Allows user-defined STP instances to be mapped to multiple VLANs.
- Up to 64 instance.
- If no instances are defined, all VLANs are mapped to instance 0.
- Same election process as STP. MST also uses the lowest BID in the network to elect the Root Bridge.
- With MST there is only one election per user-defined instance.
- MST also uses a cost value derived from the inverse bandwidth of the interface.
- When MST is enabled, RSTP is automatically enabled.

MSTP configuration

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: optional

revision rev_num

Step 5. Map your VLANs to MST instances:

instance # vlan range

verification:

show spanning-tree mst configuration

show spanning-tree mst vlan_id

CCIE Lab Scenario: if you are to ask to create 2 instance/ you just need to create 1 instance since instance 0 is already running.

configuration of root

per vlan

spanning-tree vlan # root primary/secondary

per mst

spanning-tree mst # root primary/secondary

priority

per vlan

spanning-tree vlan # priority #

per mst

spanning-tree mst # priority #