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Identifying a connected network cable 1

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keyset6

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Sep 7, 2007
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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.
 
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.
 
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.



 
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.
 
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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