Is the connection only 100Mbps


We recently have installed Cat6 cabling in our walls using Cat5e jacks (Could not find any other type). From research, this seems to be a working method, however the connection is auto-negotiated by my network switch to be only 100Mbps.

I have ruled out the following:

  • The router (Router has 4 x gigabit ports and I wired a laptop directly to it to test)
  • The laptops NIC (Network switch negotiates gigabit speed with it)
  • I have checked the wiring on the wall jacks and all color codes/numbers are in the correct spot. (T-568B)
  • I tried forcing gigabit negotiation from the laptop Device Manager settings for the NIC and the connection is still 100Mbps
  • Cables leading to/from the wall jacks (Both are Cat6 and I tested them)

Is there a way to fix this problem?

Best Answer

  • This is most likely a problem with the cabling at some point. Here are the most common problems I have found to cause this in my experience (without certified test results on the installation, which I presume you do not have):

    • Improper termination of the cable to the jack/plug.
    • Physical problem with the cabling, often the result of the cable being pulled too hard during installation.
    • Physical problem with the jacks or plug. This may be a manufacturing defect or the result of improper testing (I have often seen the pins in a jack bent when subject to the "probe" when toned out).
    • One of the network cables you are using to connect the computer to the wall could have a problem (this is far more likely if the cable is hand made or older).
    • Every once in a while you may come across a network cable that only has two pairs. They were sometimes manufactured this way because it was cheaper to do so.

    While 10-BaseT and 100-BaseTX use only two pairs, 1000-BaseT uses all four of the pairs found in your standard Cat5e or higher cabling. If any one of the eight wires has a fault of some sort, this will prevent your connection from negotiating to 1000-BaseT and result in a 100-BaseTX connection.

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