Once in a hospital's radiology department, we had this nifty security feature -- I just cannot remember the proper name to succeed at various search engines:
If a host's ethernet cable was disconnected, the uplink switch recognized this and as result declared the corresponding port as switched off, no matter if the cable was reconnected immediately. Manual interaction was required to get the link working again.
Seemed to be a useful intrusion countermeasure to prevent people from replacing hosts. Is this a standard feature I just miss to find?