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Potential break in the line? (disconnected AP)

Discussion in 'Switches, NICs and cabling' started by adambean, Feb 18, 2020.

  1. adambean

    adambean Regular Contributor

    Joined:
    Nov 19, 2012
    Messages:
    97
    Hey all,

    I'm finally redoing my home network with Ubiquiti Gear (UDM, Flex, Nano, Switches).

    I'm largely up and running, minus my second floor AP (Nano). The device works fine when I connect closer to router on a patch cable; however, it its home spot ... I only get power. It always shows up as "disconnected". When I use a laptop to test the connection, I am on LAN for maybe a few seconds every ~20-30 seconds.

    I've recut both ends, several times, even switched to a type A instead of B. Still no positive change.

    At this point, I fear that there's a break in the line somewhere. Problem is, it's a long run from my basement, up a very tight conduit, and into the attic. Before I go the path of crying and trying to pull a new line, any suggestions/thoughts?

    Thanks
     
  2. L&LD

    L&LD Part of the Furniture

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    Messages:
    11,540
    Any other 'long lines' you can test with before you start pulling cable?
     
  3. adambean

    adambean Regular Contributor

    Joined:
    Nov 19, 2012
    Messages:
    97
    There are 3 other runs going to the surrounding rooms, that all work fine. This is the one I never used, I left it for future use sitting in the attic.

    Just seems odd that ONE of the four would stop working. Two years ago I did try out setting up an AP on that line, and I'm pretty certain it worked just fine.
     
  4. Trip

    Trip Very Senior Member

    Joined:
    Aug 12, 2014
    Messages:
    1,215
    Do you have anything else you can put on the end of that cable that's PoE-powered and manageable, to test for both power and data? If so, do that to confirm if you still get power but no data on different hardware. If that's the case, and you're using UTP cable, might there be enough EMI in the path to potentially kill data, while still allowing for power? If so, you may have to re-route to avoid certain items, cross power lines at 90 degrees, etc. Short of using shielding and having to ground, for that run at least I would put in a top-quality UTP with anti-EMI jacketing, like Belden 10GXS or similar, and see if that helps. You can find shorter cut lengths of 10GXS13 on eBay for fairly reasonable cost.
     
    L&LD likes this.
  5. Smokindog

    Smokindog Senior Member

    Joined:
    Jun 30, 2016
    Messages:
    236
    Location:
    The Great State of Texas
    My neighbor had a similar issue in his house. The line down to his office would cut out every so often but a restart of the PC would "fix it". I did the same things with respect to re-terminating the ends, ... During that process I was using my trusty cable wiring tester and on VERY close inspection I would occasionally see a second LED barely illuminate as it ran the sequence. It turns out some work he had done in another room had ended up with a very slight nail nick in the wire. Fortunately it happened on a wall separating it from the attic and we were able to make a repair. I would have bet big dollars that something like that was impossible :)

    Have you used a meter to check for continuity across ALL possible pairings on both ends of the wire while disconnected?
     
    CaptainSTX, L&LD and coxhaus like this.
  6. degrub

    degrub Very Senior Member

    Joined:
    Dec 21, 2015
    Messages:
    1,018
    if it is a POE device, you could try a local power supply or perhaps a higher power injector than what is currently in place. A time delay reflectometer could help you pinpoint the weakness if that is what it is. Likely need a network installer with the TDR to come out and check it if you don't find anything obvious
     
    L&LD likes this.
  7. adambean

    adambean Regular Contributor

    Joined:
    Nov 19, 2012
    Messages:
    97
    I tried using the poe injector that came with the AP, no change. Damnit.
     
  8. degrub

    degrub Very Senior Member

    Joined:
    Dec 21, 2015
    Messages:
    1,018
    Was it high power type ?
    If you have a weak spot in the line on dc, the device may not operate correctly. Put it between the wall receptacle and the device at the device end and see.
     
  9. L&LD

    L&LD Part of the Furniture

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    What I was thinking is to put the device you want in the attic at the end of one of your other long runs and check it works as expected. ;)

    You need to check (and double-check) every part of the link to find the real cause.