A cable plugged into a switch but unconnected on the other end, might lead to any problem in a "noisy" environment (industrial)?

It's short, 50 cm, but there are motors, inverters, power supplies very close to it.

  • It is not recommended to have that, why you having this ?
    – Mr.lock
    Sep 2, 2018 at 6:01
  • The switch is inside an big enclosure and they placed an Ethernet port on the front door to connect a device without open the cabinet.
    – Mark
    Sep 2, 2018 at 6:05
  • We had some weird problems with the communication that seem to be fixed removing that cable... Hence my question.
    – Mark
    Sep 2, 2018 at 6:06
  • That is going to depend on the switch model. Different manufacturers take different shortcuts, even within their own product lines. Some manufacturers make switches that are hardened and designed to be used in industrial environments. You have not provided us enough information to answer specifically, but any metal cable will act as an antenna.
    – Ron Maupin
    Sep 2, 2018 at 14:43
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Dec 25, 2018 at 9:23

1 Answer 1


A disconnected cable shouldn't be able to cause problems.

The twisted-pair wires are connected by pulse transformers, isolating the cable from the connected devices. However, with a shielded cable and non-optimal grounding of the cabinet components, strong noise from the shield might be able to disturb system ground and cause stability problems. I'd use an unshielded cable (UTP).

On the data level, an unconnected cable cannot possibly get a link up and introduce garbage data. The link can only come up by negotiation using link pulses (FLP) - this is practically impossible through noise.

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