I think I answered my own question by labbing this out with some Catalyst switches. There are also some Meraki community conversations around this: Re: Mekari / Cisco - MSTP and RSTP Configuration Questions - The Meraki Community   What Meraki is essentially doing with the configuration is emulating RSTP. I don't think you can actually establish the same MST region between every Meraki switch. Instead, you communicate with an RSTP boundary and the behavior is the same.   When I configured the exact same Meraki MST configuration used with this new feature - and then connected it to an MST0 instance with a different name and revision number - the "Meraki" switch observed the root switch properly and this was the output:   Catalyst-Switch#show spanning-tree mst interface gigabitEthernet 0/1 GigabitEthernet0/1 of MST0 is root forwarding Edge port: no (default) port guard : none (default) Link type: point-to-point (auto) bpdu filter: disable (default) Boundary : boundary (RSTP) bpdu guard : disable (default) Bpdus sent 5, received 225 Instance Role Sts Cost Prio.Nbr Vlans mapped -------- ---- --- --------- -------- ------------------------------- 0 Root FWD 20000 128.1 1-4094   Catalyst-Switch#show spanning-tree MST0 Spanning tree enabled protocol mstp Root ID Priority 32768 Address 6899.cdc2.a680 Cost 20000 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32768 (priority 32768 sys-id-ext 0) Address ac7e.8abd.4c80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Gi0/1 Root FWD 20000 128.1 P2p Bound(RSTP) ... View more