Author Topic: Be able to test Cable while connected to a network switch?  (Read 958 times)

mo33612

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Be able to test Cable while connected to a network switch?
« on: November 30, 2016, 02:37:10 PM »
Be able to test cables while the connected to a network switch.

Pockmark

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Re: Be able to test Cable while connected to a network switch?
« Reply #1 on: December 18, 2016, 04:56:37 AM »
I don't think that's technically feasible with an analog tone generator, since it relies on radio waves. The open cable acts as an antenna, but when connected to a switch the circuit is completed and the signal goes to ground. Or something like that.

Fluke has a proprietary digital toning method called Intellitone which works on connected cables; a toner & probe kit costs about $200.

The PE has the port light blinker tool which can help trace connected cables, which is certainly better than just looking for unlit ports or unplugging cables at random, which I tried-- once.

JeremyG

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Re: Be able to test Cable while connected to a network switch?
« Reply #2 on: August 16, 2017, 05:17:01 PM »
When I read this I wasn't thinking of the Tone Test, but of the TDR and Wiremap tests. I have Meraki Switches and they can do this so I was surprised when the Pocketethernet couldn't.

BjornR1989

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Re: Be able to test Cable while connected to a network switch?
« Reply #3 on: November 07, 2017, 10:34:01 AM »
Meraki must be offering this functionality solely between two of its own devices and doing some magic switcheroo.

From the manual:
Quote
The length cannot be determined if the cable is connected to another Ethernet port, as a properly terminated connection doesn't provide signal reflections that can be measured. Also, switched on Ethernet ports on the other end can provide false results as the other device is actively transmitting signals that interfere with the measurement.

Any wiremap test uses at least two wires and probes each of the 8 wires whilst powering another one to determine what's connected to what. As there are basically 4 transformers in a NIC, i don't think there's a simple method to implement this functionality reliably.
I assume Meraki is communicating with an active device on the far end to make the test work.
TDR open/closed/length tests are possible on more devices (one of my Netgear switches for example is capable of calculating the length of a cable) but they require the far end of the cable to be fully disconnected.

Who knows... If it's possible, i'm fully supporting this idea.
I brake... For lanparties!
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