Rapid fluctuation in a port link state is called link flapping.
Link flapping is detrimental to network stability because it can trigger recalculation in spanning tree and the routing table.
If the number of port down events exceeds a configured limit during a specified interval, the system forces the port out of service.
You can configure link flap detection to control link state changes on a physical port. You can set thresholds for the number and frequency of changes allowed.
You can configure the system to take one of the following actions if changes exceed the thresholds:
send a trap
bring down the port
If changes exceed the link state change thresholds, the system generates a log entry.