Hi.
Topology in short looks like this with "access switch loop to core" multiplicated on 3 different floors:
When I remove loopback from stp errors stop showing up.
But now i have other issue - when LAG or even single link in lag between access switches is connected i got 50-60% cpu usage on all switches in network ! even on those on server side - so it looks like some storm or something. in TOP I just see bcmRX to use as mush as 40-50% of cpu.
And it is like this only on one floor.
I'm looking into STP but cannot find an issue. I think i'll need to first figure out what is the issue with that connection and then take care of that mirroring.