Don't trash that cable ... yet.

[knosso2919]

Dear Linus Community I want to share the problem that I had and how I solved it. The reason why I'm doing it is because it was relatively tricky to diagnose and because just replacing some networking component does mask it so you may think that some equipment is faulty while it may very well be just fine (also the problem may present itself again in the future if misdiagnosed and misfixed).

 

Background Story (you can safely skip this paragraph)

I had a 10/100 network at home and after watching Linus videos about upgrading to 10Gb I decided to create a roadmap to slowly upgrade my network to 10Gb, my backup solution, and my security system. Thus I started the journey by replacing Cat5 and telephone cables with Cat6a shielded cables inside the walls and Cat6a sockets (yes I was running ethernet on 4 wires telephone cables). Then I replaced my 10 and 10/100 switches with 1Gb switches (10Gb is still too expensive for the amount of components that I am replacing). Then I replaced my NAS for a more performing one. And finally I started revamping my security system to have something well integrated with cameras on a separate subnet like the video from Level1tech. 

 

It was a this point that I started shuffling components around to place them in a better position and replacing long cat5 patch cables with homemade cat6a ones. While testing the new cables all kind of weird things started to happen.

 

Symptoms of the problem

All the equipments seemed to work just fine with industrial cables but not with the DIY ones.

• It took a long time to establish a link speed and IP and finally the link was 100Mbit
• In some occasions it would grab a 1Gb link but then moving the cable a little caused the link to drop to 100Mbit or to become inactive
• The link in some occasions started to quickly shuffle between active/inactive indefinitely or by dropping to 10Mbit after a long time.
• It seemed to be very inconsistent with some computers and switches jumping to 1Gb for several test in a row just to drop to 100Mbit or to inactive after trying long enough.
• A cable would work just fine before passing it behind a bookshelf but then would drop to 100Mbit or not work at all once in position. Then the same cable would work again if pulled out but then it started misbehaving even when on the floor.

Solution

Basically after I excluded interference from the AC lines, errors in the way i made the cables, broken equipment of cables, I was pulling my airs off and almost resulted in buying additional industrial cables of the required length. But then almost randomly I started comparing visually industrial cables and DIY ones with old and new plugs. I noticed that there was a piece of the shield of the socked that was curiously aligned with the exposed ends of the DIY passthrough plug that I chopped off.

 

It was at that point that came the idea. Maybe the cables of the plug were shorting on the shield of the socket. Thus I put a piece of Insulating tape on the exposed wires and now everything works flawlessly. I wanted to share this experience so that it may help other people around. If you youse pass through plugs you may not have a broken cable in your hand, it may just be a short circuit between the plug and the socket.

 

Cheers and have a good day.

[OhioYJ]

You know I never thought about that. I had actually never used that style (pass through) until recently, and that was all my local store had left. I bought some to finish my project. I had problems with several cables despite them "testing" good with a tester. Perhaps this is why. I still don't think I'd buy the pass through style again.

[knosso2919]

Let me know if that is the case. I suspect that most "well shielded" sockets do have metal right in front of the cable. For what concerns me I'm glad that I did not buy pre-made cables otherwise I would have never known that this was even possible. As for buying new cables in the future I will probably buy industrial ones when I do have enough space and don't need particularly short or long ones, however they still seem a must when recabling in tight spaces or through holes.

[mariushm]

It also looks like your wires are in the wrong order... and that there's some extra wire inside the connector (i see a curbed wire inside the connector in first picture)

 

The correct wiring is one of the two in the picture below, but the same one on both ends of the cable  - from memory T-568B is the more commonly used.

 

 

 

You're supposed to untwist only as much as needed, then align the wires then push them through the connector until the sleeve goes under that plastic bit which locks the sleeve in place and then use the tool to install the connector.

 

 

 

Your connector doesn't look right,  it starts with brown ... it should start with green-white , green   or with orange-white, orange  ... and what's with that wire on the right

 

[knosso2919]

Thanks for the info, I indeed followed the T-568B layout except for the fact that nobody told me which was pin 1. So I did like the average caveman does and copied from an industrial cable that was working perfectly fine. That cable was indeed following the T-568B layout but with the clip pointing at me. Anyway my cables are so short that you can probably put any cable in any position and the interference would still not be enough to cause problems as long as both ends are the same. 

 

I will take pin1 into account for future cables but in this case it really was as simple as a short circuit.