Cat5 socket wiring issues

TL;DR: Yes, you can just follow the colours on the back of the sockets.

Expanded answer: Ethernet uses four pairs of wires with differential signaling. In the cable, the two wires in a pair are twisted around each other, following the colors: green and green-white, blue and blue-white, etc. The pairs have a slightly different rate of number of twists per length. That reduces crosstalk between pairs, so it's important to get the pairs right.

There are actually two ways to distribute the pairs, 568A and 568B. For a cross-over patch cable, you'd crimp one end according to 568A, and the other according to 568B. But today's hardware can automatically adjust to cross-over or straight-through connections, so getting this right is only important if you are using really old hardware.

In theory, a cross-over connection could also be made between sockets (not following the colors on one end), but you can always do the crossing over in a patch cable, if really necessary. So just following the colours in the sockets is fine.

Additional info, because this regularly trips up people: There are two kinds of Cat5 wires, a solid-core "installation" variant and a stranded "patch" variant. The solid-core "installation" variant is one you should run inside the walls and connect with the sockets in your picture. If you try to connect the stranded "patch" variant to those sockets, the connection will be bad.

Because the this variant is a bit stiffer, be careful when bending it, and don't try to put it around sharp corners.

Vice versa, most RJ45 plugs are for the stranded "patch" variant. If you try to crimp the solid-core "installation" variant, the connection is not firm and will come loose over time (or immediately, in some cases). There are special RJ45 plugs together with special crimp tools that work for the solid-core variant. So in a pinch, if you really must, you can put an RJ45 plug of those. But usually it's better to just put in a socket in this place, and use a patch cable to get a plug.

In any case, make sure to buy and use the correct type of cable with the sockets and RJ45 plugs you have.

dirkt

Posted 2017-08-16T11:43:13.840

Reputation: 11 627

2+1. Learnt something new today. VERY useful to know about the different types (stranded vs. solid core) for when doing installations vs. patch cables. – Kinnectus – 2017-08-16T12:47:19.613

For extra lulz, if you try to terminate solid core with an rj45 you can end up just outright cutting through the conductor and have it look ok but not actually in contact at all. – Kaithar – 2017-08-16T13:50:39.290

@Kaithar This is only the case if you don't use rj45 connectors intended for solid cable. These mate differently to the wires so they don't simply chop them off. – Luke G. – 2017-08-16T15:17:51.310

1@LukeG. I'd assume they're built using a better blade profile, similar to how the blades are shaped on a punch down block, but I can't honestly say I remember ever knowingly encountering that kind of plug in practice and I wouldn't entirely trust them for that application either, just on principle of how solid core behaves. – Kaithar – 2017-08-16T15:43:11.873

@LukeG that's why I said "most RJ45". I'm perfectly aware there are RJ45 jacks intended for solid core cable, together with a special crimping tool, but if you buy some jacks randomly, chances are high you'll end up with those for a patch cable. – dirkt – 2017-08-16T18:02:30.483

2Be sure to be consistent to make sure you have a reliable network, i.e., don't use 568a in one spot, then use 568b somewhere else, it will only make it difficult to keep track, and therefore difficult to troubleshoot. – Davidw – 2017-08-16T19:34:43.263

Did you mean plug where you say jack above? This is a commonly misused term, but the industry uses jack to mean the female connector. See http://www.sentinelconn.com/pl_88.html and http://www.sentinelconn.com/jacks.html

– davidmneedham – 2017-08-17T13:46:20.893

That would depend on what kind of cabling you want. Usually you'd go for straight through "between sockets". See also EIA/TIA 568A & 568B Standard

– Seth – 2017-08-16T11:51:07.720

3also, as someone who has had a lot of trouble learning to cable buy a cable tester and use that to work out if things are correct. – Journeyman Geek – 2017-08-16T12:24:37.583

I think there are two main ways to wire Ethernet in the World and depending on your location it could be one or the other most commonly used. – Pimp Juice IT – 2017-08-16T13:08:52.033

2Just about everyone uses 548B as indicated on these modules. The difference in layout is down to the routing of the wires between the punchdown and pins, the actual order of the colours to conductors is the same. – Kaithar – 2017-08-16T13:53:32.927

@Seth crossover has limited use these days where every nic seems to advertise auto MDI-X support and it's redundant in gbit anyway. – Kaithar – 2017-08-16T13:57:44.223

1Generally speaking, it makes the job go easier if you use the same style of jack everywhere on the site. Not always possible of course. – Criggie – 2017-08-16T22:32:25.767

@Kaithar well you need it whenever you want to interconnect normal "clients". Yes, MDIX does it make unnecessary (in cable) often but who knows what he's going for or what devices he got? Hence I said straight through would be the usual way to go and also the link I included points that out. – Seth – 2017-08-17T05:08:54.240

1@Seth that's a fair point, who knows what embedded kit does or doesn't support heh. Admittedly, only one end needs MDI-X if I understand the tech correctly, but who knows. – Kaithar – 2017-08-17T13:49:48.963

Cat5 socket wiring issues

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