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Interesting Problem; A Working Network, but the NIC has Separation Syndrome?

By Devcon
Nov 12, 2008
  1. While I know there must be a logical solution to this problem, I am yet to see it...

    I have a network with 9 computers. These computers are connected with a D-Link Switch through a patch panel. Internet and DHCP is retrieved from an ADSL modem connected to the switch. From the beginning this network was poorly installed. The technician was up late working and made many stupid mistakes. His wiring was atrocious, poorly planned, and a monkey could have done a better job. He even put the power cables in the same conduit as the CAT5 running parallel... Anyway, each computer is connected with a patch cable connected to an ethernet outlet on the wall. This of course terminates at the patch panel, then connecting to the switch. 7/8 computers work fine, but the last one (imagine they are all positioned in a straight line) will not connect. The NIC cannot see the switch.

    Logically, that would implicate a faulty NIC, patch cable, outlet, patch board connection, or switch jack. This is where it gets interesting... Moving the 8th computer and connecting directly to the switch, the NIC connects to the network with no problems. That rules out the NIC and the switch port. If I take computer 7, and connect it to computer 8's wall jack, it also connects fine... This should rule out the jack, patch board, and any wiring inbetween. Now, what is left to troubleshoot? Computer 8 has no problem if connected directly to the switch, but does not see a cable connection if connected to a wall jack. All of these wall jacks work properly with other computers.

    Usually, when I can't make the logical connection as to why something isn't working, it ends up being an electrical problem of some sort. While the network was wired by a *****, the electrostatic interference shouldn't be enough to interfere, especially considering 7 computers work fine. Can somebody help me to see the logic? The most logical to me, is that I made an error, but I have spent a couple hours trying different connections and verifying all of the cables.

  2. Tmagic650

    Tmagic650 TS Ambassador Posts: 17,244   +234

    Does the 8th computer have an on-board NIC or a PCI card NIC?
  3. Devcon

    Devcon TS Rookie Topic Starter Posts: 16

    It was a question of bad timing. I had previously diagnosed the problem as a bad onboard NIC. On a whim, I decided to attempt to connect the faulty computer directly to the switch fearing interference between the ethernet jack and the patch panel. This one time, I even managed to deploy an Acronis Image over the network using the onboard NIC misleading me into thinking the NIC was fine.

    Now, the NIC refuses to work regardless of being branched to the wall or switch. All wall plugs have been confirmed to be operational. While I don't know to what extent, the NIC is faulty. The device is visible, but it cannot see the network upon connecting the cable. It always says "the cable is disconnected" Kind of curious why it would stop working, work fine for a few hours, then cease to work once again, but I simply put a cheap PCI NIC in the computer to solve the problem. It is an ASRock motherboard, although I would have to look up the model number.

    Note that it has nothing to do with BIOS settings or any windows config settings. All signs point to hardware failure.
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