[c-nsp] switch port "shutdown" and "no shutdown"- what exactly happens?

[Martin T]

Hi,
rather stupid subject, but the thing is, that I have one Cisco
WS-C2950-24 switch, which has one Motorola radio device connected to
one of fast-ethernet ports:

WS-C2950-24[Fa0/1] <-> [eth]Motorola_radio_device

Problem is, that about once every 24h this connection stops forwarding
traffic. I have changed the fast-ethernet ports in WS-C2950-24 switch
and even replaced the switch with a new one, I have replaced the
Motorola_radio_device, there are no interface flaps and errors on
switch port, nothing interesting in the Motorola_radio_device log
file. Both devices are behind the proper UPS. Once the traffic between
those two devices stops, simple "shutdown" and "no shutdown" to the
switch port helps. Cat5e cable between the devices is 75m(246 feet)
long. One might suspect the cable/connectors, but on the other hand
there really are no errors on the switch port. What might cause the
issue where reinitialization of the Ethernet port reallows traffic
forwarding? Might there be a possibility to reproduce such situation
in the lab?

regards,
martin