MS425 stack to MS355 stack issues

[Terk]

Pretty simple setup.  2 MS425 switches flexible stacked (only one stack port used).  2 MS355 physically stacked.  We've created crossed switch aggregate ports on both stacks.  When we connect one link, everything is fine.  As soon as we connect the second link, everything blows up and both links go down.  Of course the event log is useless.  All I see is STP port changes, but no explanations.  Besides, it's an aggregate, so STP should be disabled automatically on the individual links.  We've removed all other links, so there are no physical loops.

[LuisCruz]

Hi Terk, sounds like BPDU guard could be enabled on either end. Can you share a screenshot of the port config on both ends?

[Terk]

I'll save myself the effort of saving and pasting screenshots.  STP guard is set to disabled on all associated ports.

[PhilipDAth]

Any reason you can't use LACP and make it loop free?

[Terk]

That's the gist of the entire issue.  I'm trying to make an aggregate (lag, lacp, whatever you want to call it) work between an MS425 stack and an MS355 stack.  When I physically plug in the second link, everything goes down.

[LuisCruz]

It can also be that the stacking of the switches is not working properly on either the 425s or 355s. You might want to try bringing up the LACP connection using a single 425 and 355 first, if this works then the problem will point to switch stacking.

[PhilipDAth]

What firmware are you running?