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Disclamer: I'm a total network noob. I'm setting up a home network. I have a small cheap gigabit switch (D-Link dlinkgo GO-SW-8G). I've placed it in a central(ish) location in my apartment and have cat5e cables laid in all the rooms. In one particular room I'm getting an orange light on the switch port when I connect it to the computer and it gives me a 100mpbs connection. The cable is almost 20 meters long. The other rooms seem to be getting the expected gigabit connection.

Now here is my question, am I hitting some cable length limit? Although I tried to dig around and read that cat5e should be fine at a length of ~20 meters (in fact they should be fine for ~100 meters, if I did my research correct).

Frankly, I suspect the problem is in the switch, however before I go and spend a bunch of money on a new switch, I would want to make sure that's the issue (also in case the issue is in the switch, could you perhaps recommend a switch, or at least what I should look for when choosing one). Your help is much appreciated.

Edit: Some additional info (which could be helpful?) - the port on the switch blinks orange for this particular room and green for the rest.

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  • Does the computer itself have a gigabit Ethernet port? Do you happen to have a cable tester (at least the cheap kind that just shows whether all pairs are connected)?
    – u1686_grawity
    Jul 25, 2019 at 12:40
  • @grawity Yes, the computer does have a gigabit Ethernet port. Unfortunately I don't have a cable tester (not sure what that looks like, will do some googling).
    – Dimitar Dimitrov
    Jul 25, 2019 at 12:42
  • Yes, 20 m should be fine for distance. Have you inspected the ends of the cable to make sure they have been connected correctly, and examined the cable to make sure it didn't get damaged when it was being installed?
    – Andrew Morton
    Jul 25, 2019 at 12:57
  • @AndrewMorton I'm not sure how exactly to examine the cable? I mean what do I look for? Whether the smaller cables match the way they're wired? Thanks for the help. As far as the cable being damaged, It's entirely possible, but I'm not sure how to test that.
    – Dimitar Dimitrov
    Jul 25, 2019 at 12:59
  • @DimitarDimitrov SImply look at it and see if the insulation is damaged anywhere. Small scrapes are to be expected, but not holes or kinks. Then make sure that the wire colours are in the correct places at the ends, and that there is no more than about 1.5 cm of untwisted wire at the ends.
    – Andrew Morton
    Jul 25, 2019 at 13:03

1 Answer 1

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  • Make sure the computer you're connecting actually supports 1 Gbps Ethernet.
  • Try to swap cables with another switch port. If the port is at fault, you'll get only 100 Mbps on it no matter what the cable length is and what's connected on the other end. If other ports give you only 100 Mbps with this cable, then the switch is probably fine.
  • Try to connect two computers directly with this long cable, without a switch. Set static IP addresses on both. Make sure both use the same network mask. On Computer 2 set Computer 1's IP as default gateway. Computer 2 should be able to ping Computer 1. Check if the connection runs at 1 Gbps. If not, it's a faulty cable.
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  • Thanks, I'll try to run some tests. Just to be clear, does it mean that the switch should be fine at such distances and the issue is most probably not with it?
    – Dimitar Dimitrov
    Jul 25, 2019 at 13:03
  • If my memory serves, your research is correct - 1 Gbps Ethernet is good over Cat5E up to 100 meters. I think I had a NAS connected with a 20m cable at some point and it worked. Physical damage of a port could cause the switch to drop to 100 Mbps on that specific port, but if other/shorter cables are good with it, then I'd assume switch is fine.
    – gronostaj
    Jul 25, 2019 at 13:40
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    Well, it turns out my issue was in the cable, went to the trouble of changing it for another one and everything worked fine. Thanks for the help, much appreciated!
    – Dimitar Dimitrov
    Jul 26, 2019 at 22:07

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