My school tried to save money, so they decide to use an installed cable for phone, CCTV, and ethernet.

I used two pairs for ethernet, one for phone, and one for a CCTV camera. The phone and camera work fine, but not the ethernet connection. Sometimes, I get an APIPA address (169.x.x), or the card shows connected, then cable disconnected.

  • That is the sort of thing you can expect; you violated the cabling standard. You aren't allowed to use a single 4-pair cable for different applications. You may do that with a 25-pair, as long as the applications aren't electrically different. Did you terminate the cable yourself? Were the proper tests run on the cable to see if it passed the test suite? How do you want us to help you? There are just too many things that be the problem. If you have the installation tests, you could add them to your question. – Ron Maupin Feb 26 '16 at 1:34
  • Many things that don't meet the standards work, despite the horror that incurs here. I myself have run 2 ethernet connections on a 4-pair cable, and up until I needed gigabit, it worked just fine for 100 Mbit. – Ecnerwal Feb 26 '16 at 2:51
  • @Ecnerwal, doing what you did, while against the standard, are two electrically compatible applications of the single cable, unlike what is in the question. – Ron Maupin Feb 26 '16 at 19:26
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 13 '17 at 18:01

The first thing I would do is disconnect the phone and CCTV temporerally. If the Ethernet suddenly starts working you have an interference problem. If not then there is some problem with the ethernet wiring.

Personally I think it's far more likely that you have a broken wire or a bad connection than an interference problem.

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