finally configured MST

It took me a while, because whenever I would go into MST mode, the switch blocked all trunks. Turned out that my problem was MST not playing nice with the PVST switches. Setting a low priority on all the instances made things work.

spanning-tree mst 0 priority 16384
spanning-tree mst 1 priority 20480

on the 3550

spanning-tree mst 0 priority 20480
spanning-tree mst 1 priority 24576

on the 2950

spanning-tree vlan 1-3 priority 32768

on the 2 2924's

You can actually do all your mst config work before turning on mst.

I'm pretty sure that your MST switches (and definitely the root) need to have a lower priority than any of the PVST or RSTP switches.

Anyhow, for what it's worth, I'm up and running

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Comments

APA

Yes MST switches will need lower priority and PVST switches will need higher priority.... Otherwise if your monitoring the terminal.... The MST switch will consistently log messages saying temporarily blocking a certain trunk port due to receiving superior STP BPDU's from a PVST\RPVST switch...

I did exactly what you configured and left the PVST priority as default........ On the MST primary root switch I used the 'spanning-tree mst (instance) root primary' - I'm certain that's the command...

Remember with MST the priority is + (the instance number) all the time.....

EG MST instance 1 priority 8192 = MST Priority of 8193

Netwurk

A.P.A wrote:

On the MST primary root switch I used the 'spanning-tree mst (instance) root primary'

That's what I had done originally. Looking back, I think I set the instance I created (mst 1) to primary and forgot about also setting mst 0.

The debug/log messages clued me into what I was doing wrong

APA

Debug is our best friend!