Two gigabit switches of identical brand and model (D-Link GO-SW-8G 8-Port) are connected. This model shows a green LED light in gigabit mode, orange in 100 mode.

The two switches connected with the cable show green on one end, orange on the other end of the cable. Both switches are connected to other 1000BT and 100BT devices, so both do work in both modes. This happens with a homemade cable as well as a pre-made Goobay CAT 5-2000 U/UTP GELB 20m PL CAT 5e network cable.

What does it mean, that they show different colors on the two ends of the cable?

  • These homemade cables? – Ramhound Feb 4 '18 at 18:03
  • Either the cable is weird or the LED is. – Zac67 Feb 5 '18 at 21:44
  • with a homemade cable, but also with this cable: amazon.de/gp/product/B003KRA2SU – dnz Feb 6 '18 at 4:50
  • Then it can only be the LED - have you tried another port or connected a 100 Mbit device to see if it shows a gigabit link? I've seen LEDs soldered in reverse... – Zac67 Feb 7 '18 at 19:15
  • I have tried with different ports of the switch and repeated the result. I also swiched the switches with the same reproducable result. – dnz Feb 14 '18 at 18:16

I believe this as being a couple possible reasons.

either some sort of

  1. strange MDIX failure (not properly crossing the extra pairs?)

  2. an IEEE auto-negotiation failure. (if you have a rj-45 continuity tester use it)

either way it would be an indication of a physical layer issue.

you mentioned that you have a home-made cable. if you have rj-45 crimps make a gigabit cross over cable, re-terminating the cable on each end. ( or re-punching if its a wall outlet.)



What can cause auto-negotiation to fail on network?

image from - https://sites.google.com/site/mullais/network/what-is-the-defference-between-cross-cable-and-straight-cable

  • Actually I have a tester. I was only able to crimp connectors successfully by using the tester. The cables kept having to connection. I will do some more testing with readymade cables. But two questions: I thought one of the advantages of modern ethernet equipment was, that you no longer need to worry about crossover? and second (the switches were delivered from the same batch) how do you test the hardware revision (apart from looking at the sticker on the switch)? – dnz Feb 28 '18 at 16:46
  • You will find that in Enterprise environment's not many engineers trust auto-negotiation, or mdi-x. It's because it can fail, rarely. But it does happen from time to time. – Tim_Stewart Feb 28 '18 at 17:49
  • Have you tried jperfing across the two switches to see what the actual throughput is? – Tim_Stewart Feb 28 '18 at 17:53

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