I'm trying to set up Gigabit Ethernet in a new building that's wired with Cat 5E cabling. There are 6 drops throughout the building but, unfortunately, each room was originally terminated with RJ11 for phone. I switched 4 of the jacks to RJ45. The drops were not terminated so I patched them together into a patch panel in the basement.

Unfortunately it seems like only one of the links reached 1GB. The others cap out at 100MB. I can observe this in a few ways: * the router shows orange link light instead of green * my cable tester only blinks green for pins 1, 2, 3, and 6

I've triple checked the wiring at both ends to make absolutely certain that both sides are using the same standard, 568B. I'm not an expert but the wiring looks fairly clean to me.

Here's a photo of the patch panel: patch panel and here's the wall socket: wall socket

Possibly related is that the Gigabit link is to the first floor while the 100MB ones go to floors two and three. I suppose it's possible that there's a bend above floor 1 stressing the cables but it seems unlikely that 3 cables would fail the same way like this. I would expect a wiring issue to prevent the cables from working entirely. This is a new building so I'd be surprised if the cabling was installed incorrectly in the first place.

How can I debug this further?

  • 2
    Are the runs over 300ft? Is there any 100MB switches in between that are bottlenecking it? Maybe try redoing the punchdowns/connectors once more.
    – Narzard
    Nov 25, 2016 at 17:21
  • 2
    Are you sure you have the color coding correct at both ends? are the cables really twisted pair for a CAT5e cable?
    – LPChip
    Nov 25, 2016 at 17:27
  • 3
    @BrianF There has to be a reason that the cable testers are not lighting up those pairs, and even a hard bend shouldn't stop them from lighting up. Unless the bend was so hard the copper snapped? If you are 100% positive the wires are wired correctly on both ends, not sure what else it could be aside from a physical wire separation.
    – Narzard
    Nov 25, 2016 at 17:56
  • 1
    Can you take small pictures termination in patch panel and socket? Do you check patchcords? Nov 25, 2016 at 18:23
  • 2
    I would bet on a "telephone" wired patch between the central location and floors 2&3, if you have only two pairs connecting.
    – Ecnerwal
    Nov 26, 2016 at 15:35

3 Answers 3


Use tester with you can find out type and the position of the failure, tor example TL-828-A


You stated the building was new. Do you know who punched down the runs? Was it a network cable installer? or was it an electrician? I would re-punch the patch panel as a couple of those look out of spec from your photos. Your terms should be as close to the jacket as possible with the twist in contact.


Well I'll leave the answer here in case it ever helps someone else.

As I was testing various sockets it dawned on me that I wasn't just using a cable tester, I was also using a patch cable. Sure enough the cable was only Cat 5. Replacing that cable with Cat 5e fixed the problem. I must have swapped test cables between the first and second floors.

  • Cat 5 can be used on 1Gbps network, but need all 4 pairs. Some low quality cat 5 patch can have only 2 pairs connected. Dec 4, 2016 at 21:31

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