Cable Diagnostics with GigE

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JustJoe
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Cable Diagnostics with GigE

Tue Mar 10, 2015 3:47 pm

OK, maybe this was misleading due to a typo or omission but from the "Plugging equipment into powered port" thread:

sirhc wrote:...

So with that being said we have adopted the policy at our WISP that we turn power off to a POE port before unplugging and plugging them in and if it is a new cable, jumper or radio we FIRST run the cable diagnostics to insure there are NO CROSS SHORTS reported. We apply power back to the POE port once the cable is plugged in and or we run a diagnostics on the cable first if a new cable or radio.

If you have a 1G device plugged into the port cable diagnostics should report all 4 pairs as OK and all 4 pairs should report the same length or close to same length.

If you are powering a 100M device like the airMAX radios you should get OK OK for pairs 1 and 2 and SHORT SHORT for pairs 2 and 4 with all 4 pairs the same or close to the same length. Pairs 3 and 4 reporting as "SHORT" is OK as the blue and blue/white wires are shorted together and the same for the brown and brown/white wires, this is NORMAL.

...


So I take a new WS-8-250-AC, v1.1.0, factory default, (so all POE ports are off)

1) Plug a PC into port 1 for access.
2) Use a straight cable to connect a new NanoBridge M5 (10/100Mb) into port 6.
3) Run Cable Diagnostics on port 6.
4) Results: OK OK Short Short

Results match description perfectly.

5) Use a straight cable to connect a new NanoBeam M5-400 (10/100/1000Mb) into port 7.
6) Run Cable Diagnostics on port 7.
7) Results: Open Open Open Open (as if cable was disconnected)

Expected results: "should report all 4 pairs as OK"

Same results on GigE ports of Ti-RM5 and MicroTik RB-750GL even with 10' shielded Cat5E.

The only way to see OK OK OK OK on GigE device is if it is first powered, which is kinda hard on a NBeM5-400 without POE ...Catch-22.

If you meant to say the 10/100 radios will test correct either way, but the GigE's needed to be tested twice, the post was confusing and could at least use some editing.

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sirhc
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Re: Cable Diagnostics with GigE

Tue Mar 10, 2015 3:55 pm

Thats a good point Joe, a slight oversight on my part.
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JustJoe
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Re: Cable Diagnostics with GigE

Tue Mar 10, 2015 4:32 pm

I guess it's not surprising, you had so much info packed into that one post.

This is the kind of thing that eventually deserves to be an article in a reference manual wiki, where it can evolve to be a concise set of steps followed by a motive explanation. That way you can point back to it instead of trying to recreate it with every post. :wink:

Understand that I spent a lot of time making sure it wasn't bad cable or radio. Didn't want you yelling at me for doing it wrong. :yikes:

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