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Identifying a connected network cable

Identifying a connected network cable

Identifying a connected network cable

I'm an old school telecom/PBX guy, but these days of course involved with networking in a basic form at least with VoIP. I've used a network cable tester after connecting plugs and jacks plenty of times, but Is there a device that could plug into a network jack that would ID the port that it's on? Had a customer who's downsizing that wanted to disconnect phone and data connections in a vacated part of the building. As suspected, most of the data jacks weren't labelled on the patch panel. When toning a cable connected to a PBX line, if a phone couldn't be plugged in to identify the line/port due to it being defective or deactivated I'd use an open pair to be able to hear the tone better. I've had success with hearing a tone on a cable connected to a PBX port, difficult but listening very carefully is not impossible. With a network port though, it brought the tone down to nothing on a given pair. I then put the tone on pins 1 & 4, the test tone seemed to be a bit less muted not being on a dedicated pair. It was very low, but I found it. No luck with others. For those I hated to do this but I ended up by trial & error unplugging network ports that were inactive, a few at a time until the jack was dead. A lot of walking back & forth, sure would have been easier with 2 people to watch network port lights on a device.

Is there some kind of utility on the switch/router that would indicate which port a test device is plugged into, or simply an app for a PC that could indicate the port it's on? Or - something like the intercoms from years ago that would use the house AC wiring to transport audio, maybe it was a carrier signal that rode on the AC wiring. Makes me think of an old 'Carrier Current' AM radio station on a college campus. There's got to be an easier way than what I did today.

RE: Identifying a connected network cable

Most of the manufacturers who make real cable or network test equipment (not continuity testers) have an option to "blink" the port, which just brings the link up/down.

On a few jobs, I have just written a script on my laptop that does the same thing (On for 2 sec, Off for 5 sec, etc). If you are dealing with a managed switch, you can plug your laptop in and just find what port it's MAC address is on.

RE: Identifying a connected network cable

That 'blinking' technique is a good idea, whether using a dedicated device or a script on a laptop. Ideally, the customer would have a managed switch.

I'll check out the Link Runner.

RE: Identifying a connected network cable

Blinking a port works on low density switches, or when you don't have many devices connected. If you have three cascaded 48 port switches in a rack that are all fully patched with numerous active ports, blinking a port is dang near impossible to locate. the LinkRunner works well, and my guys swear by them.

RE: Identifying a connected network cable

Yes, the blinking port method would have been Ok where I was, not a huge system. We have a network cable tester, off hand don't recall what brand but it wouldn't power on with the battery from my basic telecom tone generator. I need to try it again with a new battery. Looks like the LinkRunner is the way to go.

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