2

This question is about cabling quality problems in a Cat7 (10Gbps) network installation in an industrial environment, where fiddly M12 x-coded 8-pin connectors are used. In some cases, we are also running PoE over the cables.

During the installation of the (pre-measured / certified) cables, single pins within the M12 connector can get bent or don't contact properly. As a result, the LINK/ACT LEDs are blinking fine and PoE supply is okay, but at a closer look the transmission mode falls back from the desired 10000Full to 10Half, combined with huge packet loss.

Looking at the bad (Ethernet) frame counters on both ends of the cables, we often see an asymmetry:

  • ~0 bad frames from A to B
  • 10000s of bad frames B to A (opposite direction)

At a first glance, this sounds to me as if this could indicate a problem on a certain Rx or Tx wire pair within the cable. But I am really not an expert in Ethernet physics.

So, question: Is there any way to conclude which of the 8 pins or wires in the Cat7 cable are defective, from the observed asymmetry in bad Ethernet frame counters?

I know that you can actually measure the wires. That's been done. But the problems only arise once the connectors get plugged. So I am explicitly looking for other debugging means.

rikinet
  • 33
  • 4
  • If the wires test OK, perhaps the problem is with the connectors? Maybe a wire isn't making good contact, or the connector is just miswired? – Michael Hampton Sep 25 '20 at 16:56
  • @MichaelHampton - The problem is _definitely_ with the connectors, and I know that it is almost certainly caused by pin(s) not having proper contact. The question is: Which one(s)? Can the bad frame counters tell me? – rikinet Sep 27 '20 at 20:00

0 Answers0