Ideal MSTP configuration for Cisco switches to interoperate with Meraki?

[Nater]

I'm trying to resolve an STP problem which has taken our whole network down the last two days, and I want to make sure I have the ideal MSTP configuration on our Catalyst 6509 for interoperating with all our switches, especially Meraki but also some legacy HP.

Initially I had this configuration on our core switch when I transitioned it from PVST to MSTP:

spanning-tree mode mst
spanning-tree extend system-id
spanning-tree mst 0-1 priority 8192
spanning-tree vlan 1-4094 priority 8192

We're a school district, and I set this up during the summer when very few staff were in the buildings. Reading up on  MSTP there were suggestions about creating regions and instances, so I added this:

spanning-tree mst configuration
name region1
instance 1 vlan 3-4, 6-8, 12-16, 100, 110, 120, 200, 300, 999-1000

I didn't see effects, positive or negative, to adding this. Are they necessary or helpful in any way, or should I just remove the region and instance to the core switch?

For further mitigation today I added "spanning-tree guard root" to all ports on the Catalyst 6509 and added this to the config:

spanning-tree portfast edge bpduguard default  

I'm hoping this will help prevent spanning tree from going totally haywire again.

[GreenMan]

This is from the Advanced MS Setup Guide:

Meraki switches do not support MSTP but are compatible and will see all MSTP instances as a single RSTP region.  [0]

You will, I'm sure, need to revert to a single instance, with something like:

spanning-tree mst 0 priority 8192

have a good read here:  https://documentation.meraki.com/MS/Deployment_Guides/Advanced_MS_Setup_Guide#Protocol_interoperabil...   and here:

https://documentation.meraki.com/MS/Port_and_VLAN_Configuration/Configuring_Spanning_Tree_on_Meraki_...

If in doubt, I'd suggest raising a case with Meraki Support.

[Tony-Sydney-AU]

@GreenMan is right. Be sure to use MST 0 (instance 0) for compatibility. This was discussed before on this other thread.