RSTP and MST interoperabilty

[Arshad Safrulla]

The project I am working on requires to connect one Meraki switch with 2 Cisco Catalyst 2960X switches. Meraki Switches support only RSTP/STP meanwhile Catalyst supports PVST/MST. In this case I believe best scenario is to have MST running in Catalyst so RSTP will be compatible from Meraki side. 

But I am in a position where I have to change the default native vlan from 1 to something else. In this case what would be the suggested configuration from Catalyst switch side? 

I am thinking to have Native VLAN mapped to MST instance 0. Is this the right practice? Your valuable feedback is highly appreciated.

[paul driver]

Hello

MS's are compatible with rapid pvst+ ( 802.1w) on the 2960x

[Arshad Safrulla]

But the problem is when I use a VLAN other than 1 as Native VLAN. How the STP will behave?

[paul driver · Accepted solution]

Hello

As these are both cisco products and rstp is compatible between both all should be fine, One misconception is that specifying a native vlan is switch specific which is incorrect its link specific

[Peter Paluch · Accepted solution]

Hi Arshad, hi Paul,

Please allow me to join.

Arshad, let me clarify: The 2960X switches support PVST+ (falls back to legacy STP on access ports), Rapid PVST+ (falls back to RSTP on access ports), and MST. I do not know about the Meraki switches but you are saying that they only support STP and RSTP, not MSTP or the per-VLAN STP variants. Am I correct here?

In that case, I would suggest that for simplicity reasons, you keep your Catalyst 2960X on Rapid PVST+ and Meraki on RSTP. Regardless of the native VLAN used on your trunks toward Meraki switches, the 2960X will send out a standard untagged IEEE RSTP BPDU out of its trunks with its contents derived from VLAN1. This BPDU will be used by the Meraki switches to interoperate their RSTP with your Rapid PVST+. The Rapid PVST+ BPDUs will be simply flooded through the Meraki switches and not processed, but the IEEE RSTP BPDUs will be processed normally.

In my opinion, there is no value in running MSTP on your Catalyst 2960X just to interoperate with Meraki. The Rapid PVST+ is capable of doing it just as well, and quite frankly, Rapid PVST+ is still easier to maintain. Especially if you do not have tens or hundreds of VLANs, you would probably be better off with running Rapid PVST+ (if you do have tens/hundreds of VLANs, that may be a different story, though).

Please feel welcome to ask further!

Best regards,
Peter

[paul driver]

Hello Peter

Your very welcome..

Meraki Documentation
Please note that the MS series is compatible with industry standard STP (IEEE 802.1D and RSTP (IEEE 802.1w) and runs RSTP by default. MS switches do not currently run MSTP (IEEE 802.1s),

[Peter Paluch · Accepted solution]

Hi Paul,

Awesome, thanks!

Would you agree, then, that probably the easiest way to go would be to have the Cat2960X run RPVST+ and the Meraki run RSTP? Because these two protocols can still talk to each other on an equal level (sans per-VLAN semantics on the Meraki side). If we introduce MSTP, we introduce a lot of added complexity, and as far as the Catalyst/Meraki interoperation goes, I see no advantage to it.

Best regards,
Peter