Symptom
device crash and the following information on tracelog:
========= Exception Tracebacks =================================================
Exception to Fastpath Thread:
Frame pointer 0xFF86669DA0, PC = 0xFFD85AB5C4
IOS Thread backtrace:
UNIX-EXT-SIGNAL: User defined signal 2(17), Process = Spanning Tree <<<<<<<<
Conditions
The trigger for the issue would be changes in the spanning tree data due to port flap , fwding state change.
Also the probability of this is very less as it is a race condition. It is also seen only in Cat3k
