spanning tree recalculating

[mikeynorrish]

I had a similar problem with 5300 and 2650 switches. All spanning tree ports were set as edge and bpdu-filtered.

The problem seemed to be that there were a few ports which didn't have the speed-duplex forced. Also, by turning on debugging (debug dest sess, debug events) I found a few interfaces which weren't stable - one involved swapping a mini-GBIC and the other, which was a gig copper link, just had to be shutdown at both ends. The switches will have to be swapped out for this one. It took me the best part of a day to trace the problems but I think that's done it for now . .