Re: Spanning tree instances on a old switches and newer ones
Regarding the maximum number of MST instances, I don't know any particular command for that. Usually, this limit is described in the Configuration Guide for the particular switch platform and IOS version. Have you had a look there? Let me know the switch type and IOS version and I'll gladly point you towards the proper document.
The MSTP and 802.1D or PVST/PVST+ cooperation is a complicated topic. I suggest reading these documents:
In a very short summary: if the outside world is pure 802.1D then only the MST instance 0 interacts with the outside world, and the state of the boundary port (Blocking/Discarding, Forwarding) influences all instances (and therefore, all VLANs).
If the outside world is PVST/RPVST then the boundary port replicates MST instance 0 BPDUs onto outgoing PVST/RPVST BPDUs on all known VLANs, and maps the incoming PVST/RPVST BPDUs onto the MST instance 0. There are some things that must be met in order for this "PVST Simulation" to work properly - see the referenced documents for more information.
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
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