Mekari / Cisco - MSTP and RSTP Configuration Questions

[Qman]

I have been task with configuring STP for one of our customers and looking for some direction on how to configure the environment. The topology consist of Cisco 4506 devices on the end and Meraki MS425-32 and MS120-24 in the middle. I will be implementing MSTP and from the information I found doing my research, Meraki doesn't support

MST but is compatible and will see the traffic as one instance. From the information I have found to make the Meraki devices the root? Once the traffic passes through the Meraki devices the 4506 will re-elect a root bridge for the instance. So, if someone can inform on how to approach the configuration it will be greatly appreciated. My thoughts are below. Also, are there firmware concerns?

<cisco enterprise switch> -- <meraki switch> -- <cisco enterprise switch>

1. Configure the Cisco 4506 for MST only one instance for vlans

2. Configure the Mekari devices for RSTP

3. Make the Mekari devices the root\secondary for the vlans (several)

4. Set spanning-tree priority on one of the Cisco 4506 to elect preferred root bridge for MST instance

5. Include native or vlan 1 in the instance as the Mekari devices uses for processing ?

[PhilipDAth]

That sounds good to me.  If you have modified the spanning tree priority on the Meraki switches to makes them root you shouldn't need to mess around with priorities on the 4506.

[debo]

Would you use mst instance 0 or 1 . I understand it should be single instance but i see some suggest using 1 and others 0 

thanks

[Qman]

Hi,

I was going to use instance 1 can you tell me what would be the difference between the default 0 instance?

Thanks,

[PhilipDAth]

I would only use the defauly instance in this case.  So all you need to do is:

spanning-tree mode mst

[DCC]

hi, in summary, if i want to have a meraki switch as root bridge, with catalyst access switches, is it enough to enable mst mode (spanning-tree mode mst) on catalyst switches?

[debo]

@DCC yes just enable mst on ALL catalyst switches hanging off the meraki core. The keyword is ALL. hope it helps 

[GIdenJoe]

On the Cisco side it's always best practice to not only enable MST but also to put all Catalyst switches in the same region (by matching name, rev number and Instance to VLAN mapping).

Then you will have a clear boundary between the Meraki switches and the Catalyst switches.

Normally it is NOT best practice to use IST ( = MST 0) for VLAN mapping but with interconnecting to Meraki which only supports RSTP in case of classic MS switches you shouldn't have any potential PVST simulation error crap 😉

Be sure to allow VLAN 1 ( I know, strange) over the trunks so the interaction between MST and RSTP goes smoothly.