I have a box of bulk Cat5e riser cable left over from when I had my house wired. I figured I could use this to make some custom length cables for connecting my computers, switches, etc. I had a crimper already so I bought a bag of RJ45 plugs. I made a few cables several years ago, but my experience/knowledge with this sort of thing is minimal.

None of my cables are working. I don't have a tester so I just plug the cable into a computer and switch but I get no link light. I wired them them all straight-through (T568A) and visual inspection doesn't show any problems.

Any ideas what I might be doing wrong?

Update: I just ordered a cheap cable tester on eBay so maybe that will help.

  • Just out of curiosity, what did the cable tester say? Were you able to get your cables working?
    – rob
    Apr 17, 2010 at 0:32
  • The cable tester showed that some of the wires were not connecting. I also bought a new crimper but I'm not sure that helped. It seems like my main problem was that some of the wires where not getting far enough in. I started striping the cable jacket further back so I can get a better hold on the wires. I now have working cables! Thanks for all the suggestions.
    – stu42j
    Sep 24, 2010 at 15:08
  • Glad you got them working!
    – rob
    Oct 4, 2010 at 19:08

7 Answers 7


Double-check that the ends are on all the way. When you look through the end of the connector, you should be able to see the shiny copper tips of all the wires flush with the end of the connector.

If that's not the problem, it might be that you're getting crosstalk if you didn't follow the proper pinout.

Be sure to wire them correctly, according to the TIA-586B standard. There's a howto at http://www.edpscomputing.com/network.htm which you can use (scroll to the bottom).


The other answers hinted at this, but I'm going to underscore it:

Pins 4 & 5 (the centermost two pins) must be on the same twisted pair.

Pins 3 & 6 (the pins just outside of 4 & 5) must be on the same twisted pair.

If you wired it "straight-through" as you said, without knowing about the special pairing requirements, then you probably did your pairs like this: (1 & 2), (3 & 4), (5 & 6), (7 & 8). That just won't work. You would've got pins 1, 2, 7, and 8 right, but pins 3, 4, 5, and 6 would be wrong. (I'll spare you the details of balanced-line transmission and noise cancellation.)

So follow the TIA/EIA-568-B standard as rob mentioned. Not only will it get the pairings right, but it'll make it easier when you or someone else has to work on those cables again.

One other thought: Inside the RJ-45 plugs, you know the little teeth that pierce through the insulation of the individual wires? The design of those teeth can be optimized for solid conductor wire, or optimized for stranded wire, or designed to work okay with either. If you happened to get the kind of RJ-45 plugs with teeth optimized for the opposite kind of wire from what you're using them on, they may not work reliably.

  • I remember a local cybercafe owner who wanted to make more money by selling hardware, like for example "home made" network cables. Yes, he was actually selling "straight" cables, without understanding why people were returning all of them.
    – Gnoupi
    Apr 2, 2010 at 18:26
  • I wired them using T568A. By straight-through, I simply meant "not cross-over". That's for the suggestion though.
    – stu42j
    Apr 2, 2010 at 18:45

It going to be hard to tell you what exactly you did wrong. My advice would be to cut the plugs off and start over following a guide like this one from Lanshack.


Ok maybe I'm overthinking it, but as another poster said this is going to be hard for us to debug. You could get a multimeter and do a continuity check to figure out which pin on one end is wired to which pin on the other end. Then check to make sure it's TIA-586A|B. It'll also tell you whether you're making contact at all.

If the cable is as you expect electrically, then I would start looking at things like interference or cable length. Are they too short? Too long? Bad shielding? I can't imagine simple interference is preventing a link light, so it's probably not electrically connected.


I've just learned how to make these cables at work, and I've had good luck so far, so let me tell you the procedure I use:

  1. Carefully strip about an inch and a half of outer plastic from the cable
  2. straighten out each of the individual wires and get them in the proper order. Spiff listed the order correctly, or you can google the specification to get the "official" color ordering. (note: the actual color doesn't matter, just that the colors are paired and both cable ends are identical)
  3. NOW is the time to trim the wires to length; You should trim them to about a centimeter, or you can look at an RJ45 head for guidance. The wires should be long enough to reach the end of the canal so the gold heads can be pushed into them when crimped, and the outer sheath should be in position to be grabbed by the square hole thingy on top of the head.
  4. Stick your head on and double check to make sure that the wires reach all the way down the canal so it gets properly crimped.
  5. CRIMP! Squeeze it down all the way and make sure you seal it tight. Then visually inspect everything for a tight seal, and test once you have your testing unit. Hopefully it should work.

Crimpin' people, now that's what it's all about, yo.


Wire colors: wo = white orange o = orange wg = white green bl = blue wbl = white blue g = green wbr = white brown b = brown

Pin out for CAT-5 Plug = wo o wg bl wbl g wbr b

RJ45 for an Ethernet jack (Ethernet is on 1-2-3-6): 1=wo 2=o 3=wg 6=g

Crossover: 1-3 and 2-6 are reversed (order is 3 6 1 4 5 2 instead of 1 2 3 4 5 6)


I know you already commented that you did wire T568, but for anyone that isn't aware of how to crimp Cat5 cables, wikipedia has a good explanation:


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