Ethernet wall socket works with some devices and not others

[terenceterence]

I recently moved into a quite modern flat. The master ADSL socket is in a cupboard in the hallway, so that's where I placed the ADSL modem/router. In the same cupboard is a bank of ethernet sockets, each labelled 'lounge' ,'bedroom 1' 'bedroom 2' etc, and there is an ethernet wall socket in each of the corresponding rooms. So I naturally connected ethernet Cat5e cables from the modem/router to each labelled socket in the cupboard, expecting to be able to use the wall sockets in each room. When I connected my wife's laptop running Windows (8 or 9?) to the wall socket in the lounge, it connected to the internet via the cabled ethernet without problems. But when I did the same thing with my own laptop running Linux, or when I connected my BT Youview TV box to the wall socket, neither device could connect to the internet. Does anyone have any idea why one device can get an internet connection via the wall socket, but other devices can't? (Everything always works if I directly connect an ethernet cable to the router; it's only the wall socket that has problems.) Of course, one solution would be to get powerline adpators, but this would be a waste when there seems to be a professionally wired system in place.

I should also add that I've tried using different patch cables at both ends (router to labelled socket in cupboard, wall socket in room to device), all with the same results, so I'm pretty sure the problem isn't just a bad cable.

 

[bill001g]

You never really know who wired things especially in a apartment. They may have just used one of those cheap 1-8 continuity tester things. The hardest problem is when the wires are connected but they do not make good enough contact. This means some device can tolerate it and other can not.

Unfortunately the meters that can do extensive testing cost a lot so many so called network cable installers do not buy them. The price puts it out of reach of most end users also.

I would see if you can look at the wires and see if they appear to be connected well and of course with the correct color pattern on both ends. The only thing you can try after that is to pull the wires out of the jack and panel and reterminate them. Most time you need a fairly inexpensive punch down tool to insert the wires.

 

[terenceterence]

You never really know who wired things especially in a apartment. They may have just used one of those cheap 1-8 continuity tester things. The hardest problem is when the wires are connected but they do not make good enough contact. This means some device can tolerate it and other can not.

Unfortunately the meters that can do extensive testing cost a lot so many so called network cable installers do not buy them. The price puts it out of reach of most end users also.

I would see if you can look at the wires and see if they appear to be connected well and of course with the correct color pattern on both ends. The only thing you can try after that is to pull the wires out of the jack and panel and reterminate them. Most time you need a fairly inexpensive punch down tool to insert the wires.

Hi bill001g, thanks for your reply. Having seen a similar thread on this forum
http://www.tomshardware.co.uk/answers/id-2669252/problem-trouble-ethernet-connection-rooms-computers-rooms-computers.html
the next thing I was going to try is to check the wiring connections behind the socket. I'll report back once I've tried your suggestions.

 

[Solandri]

IDoes anyone have any idea why one device can get an internet connection via the wall socket, but other devices can't?

The most common cause I've found for the problem you're seeing is that a contractor who knows nothing about ethernet rigged up the in-wall wiring. Conceptually it's the same as RJ11 (phone) wiring, so many contractors think they know how to do ethernet. Unfortunately, the wire order isn't just all four pairs in sequence (12, 34, 56, 78). The middle two pairs are split (12, 3, 56, 4, 78).

https://www.handymanhowto.com/wp-content/uploads/2015/08/TIA-EIA-568B-Ethernet-RJ45-Plug-Wiring-Diagram.png

If you wire it incorrectly as (12, 34, 56, 78), the two middle pairs (34 and 56) end up traveling on different twisted pairs, compromising their noise cancellation. If the device you connect to that wall socket puts out a strong voltage ethernet signal, it's able to overcome the additional noise and the device works fine. If the device doesn't put out as strong a voltage, then the noise overcomes the signal and either you get a slow connection, an intermittent connection, or no connection.

A cable tester should pick this up. The fix is pretty simple - rewire the keystones on both sides. In fact the keystones are usually labeled with where to put the color pair wires, so I'm not really sure how contractors keep screwing this up. Here's a pic of what a keystone (the other side of the ethernet socket) looks like.

http://images.pcworld.com/howto/graphics/205913-keystone_wiring_606_original.jpg

But it seems not all of them map the same locations to the same wires. The one used in this site splits the blue and green pairs. So it's really important to follow the color-coded label.

https://www.handymanhowto.com/how-to-install-an-ethernet-jack-for-a-home-network/

 

[terenceterence]

Thanks for both answers. I've checked the wiring behind the sockets and it looks fine. All the wires are slotted into the corresponding colour-coded slots and appear to sit securely within the slots. Moreover the keystones at both ends have only 1 colour against each slot, rather than A and B colour patterns as in some keystones, so there is no possibility of different wiring schemes having been mixed up. Also, the outer insulation of the cable has been stripped back just enough to allow the coloured wires to be connected, so I don't think the problem is caused by too much un-twisting. All in all, it looks like a neat professional job. Of course, just by looking at the wires doesn't tell me how good the actual contacts are, so I guess the next thing to try is to re-terminate the wires. For that, I'll first have to get a punch down tool.

 

[terenceterence]

Latest update: it seems that just by unscrewing one of the wall sockets to check the wiring, thereby jiggling some of the wires about a bit, has made that socket work! So it seems like it's definitely a problem with some of the contacts. Here's hoping the sockets in the other rooms work; if not I'll try the same thing.