We have a new office that was punched down with Ethernet in every office and every cubicle. The electrician didn't mark the ports on the patch panel or the wall ports, so I don't know where say port 1 on the patch panel goes in the office.

I've heard of people using a tone generator to figure out where the cables are but I'm not sure what that entails. I was also thinking of looking up ARP entries on our switches to find out what port is getting what MAC address and then cross referencing it with a list of MAC addresses on all of the PCs in the office. This sounds unreliable though.

Is there a quick and easy way to label these ports?


You're better off using a tone generator/probe kit. It's going to be quicker in the long run and less prone to incorrect results.

I would suggest using a different wiring contractor next time and specifiying that you need them to label the ports at the jack and the patch panel.

  • Also some cable continuity testers will generate tones as well, so you can do continuity testing while using a tone probe to sort through the mess of cables. – Red Tux May 10 '11 at 2:12
  • Here is an example of one that does tones and continuity for both cat5e/6 (RJ45) and coax (BNC). Should make testing from port to port easy, even for an inexperienced tester. amazon.com/dp/B00006HO7S/… – MaQleod May 10 '11 at 2:48
  • You can get chinese knockoffs of these on ebay for $15. I've got one; it works fine. – BlueRaja May 10 '11 at 6:10

Check whether or not the job specs have actually been met, as it may be possible to get the electricians back to finish the job.

Either way, I suspect that if the points aren't labelled no testing was done either, so if you need to obtain a cable tracer (probe & injector) try and get one that will perform at least basic tests as well.

Using a tracer is child's play. Plug the injector into a port and then use the probe to follow the signal. It's only when you need to work in tight bundles that things can become a little tricky.

In the future, if you get a say in it, ensure the job specs include proper testing and labeling, not just running the cables. The relatively small extra cost is well justified and can save you many hours of frustration.

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    A competent low voltage tech would test and label regardless of what his papers say. – MaQleod May 10 '11 at 3:14
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    @MaQleod, I think you will find that this kind of thing differs from place to place. Over here a contractor, of any kind, will do what he has been contracted for and nothing more. Maybe the profit margin is more generous where you are, leaving room for them to do that little extra. – John Gardeniers May 10 '11 at 3:22
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    I honestly don't know about profit margin, I just know whenever I wired buildings, I tested and labeled everything before leaving, regardless of whether that was specified or not, as it is part of the job of cabling. Out of all the companies I've worked for while wiring, that was the case, and that was across 4 different states. Maybe it is just a US thing. To me though, cabling means running, terminating, testing and labeling, nothing less. – MaQleod May 10 '11 at 3:25
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    @MaQleod - of course, you're also the kind of person donating their time to others on Server Fault ;) If an electrician is dodgey enough not to label their work, I don't think they're the kind of person to hang out here (nor would we want them to, I suspect) – Mark Henderson May 10 '11 at 7:30
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    I'd think that the time spent for testing and labelling also counts as billable hours. – Simon Richter May 10 '11 at 10:22

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