We're building ethernet cable or a non-profit community computer lab. We test them with a cheapie cable tester, which I believes simple checks the electrical connection of each wire. We're having some problems with the networking ( pings are variably iffy ) , and we'd like to test the cables more thoroughly -- but of course, we can't afford a better tester.

Is there were some program that could use network cards on two computers to do more sophisticated testing of a network cable, on the physical layer?

  • Get a better cable tester. There is no magic to cat5 cable making, crimp the ends properly and test. – DanBig Nov 19 '09 at 16:09
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    Are you really saving that much money by making them yourselves instead of purchasing them pre-made from some place like monoprice.com. I haven't checked prices on bulk cable in a while, so I honestly don't know. I also don't know what size runs you're making. – Ryan Bolger Nov 19 '09 at 16:14
  • Agreed, monoprice is my go-to place for cables. – EEAA Nov 19 '09 at 17:18
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    IIRC, we had a whole spool of cable donated. – user26664 Nov 19 '09 at 18:34
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    @RyanBolger: Seriously people, what DO you have against others trying to do without professional-level expensive equipment? What if I JUST want to know if there are any faults in THAT particular cable?! What's wrong with aspiring to use readymade hardware NICs to do this? – Milind R Nov 8 '14 at 6:07

No, generally speaking, you're not going to find applications that are worthwhile to test a cable using two PC's.

You really need a dedicated cat5/5e/6 cable tester. Decent cable testers can easily be in the $2k+ range depending on what type of testing you require, ie certification, crosstalk, near end, far end, alien, etc.

Either buy off the shelf premade cables or double check how you are making your cables

So many people make the mistake when making ethernet cables that they ignore the COLORS and stripes on each wire. This matters. You need to get both PINNING and PAIRING correct.

Pinning means 1-1, 2-2, 3-3, etc... or maybe 1-3, 2-6, 3-1, 6-2 for 10/100m crossover.

Gigabit copper is even more demanding.

PAIRING, on the other hand make sure that PINS 1 & 2 are a pair (meaning if pin 1 is orange, pin 2 is orange/white stripe), 3 & 6, 4 & 5, and 7 & 8.

99% of the most common mistake take 1 & 2 as a pair, and 3 & 4 as a pair. YOU WILL DEFINITELY HAVE PROBLEMS if you do this. Just look at one of the cable and read off your colors. If you have the same color wire on 3 and 4(say green and green/white), you know you've screwed up.

Another tip, when making cables make sure that when you look through the front of the connector you can see the shiny copper tips of the cable. This will tell you the individual wires are fully seated and ready for crimping.


  • Thanks you! It baffled be why it didn't work with all 8 wires connected and tested with a (conventional electrical) tester. Turns out I was making the 99% mistake with pairing. What is interesting though I asked a friend who did a lot of cabling for his home network and he didn't know this and it worked for him. Maybe he just did this accidentally without being consciously aware... – axk Oct 18 '14 at 13:10
  • See serverfault.com/questions/86326/… – Milind R Nov 8 '14 at 6:08

This isn't exactly what you're looking for, but to test cables in the past, I've just patched two computers directly together and fired up Iperf to make sure I'm getting something close to the expected bandwidth between the two systems. While running the test, I'll sometimes move the cable around a bit to make sure that the ends are terminated securely.

  • This is a good, expedient, way to tackle this problem- it will work for your current environment. However, not all wiring mistakes will be detected by this approach- not all of the pairs are used by ethernet. You can end up in a situation where the cable works fine for ethernet, but fails for PoE, for instance. – Tim Howland Nov 19 '09 at 16:20
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    @Tim - GigE requires all 4 pairs. – EEAA Nov 19 '09 at 16:26
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    Fair enough- still, I doubt the non-profit community computer lab above is going to be springing for Gig-e... – Tim Howland Nov 19 '09 at 17:26

I've had good results from the Test-Um Lanscaper tool- it does physical checks (wiring pattern, continuity, capacitance, length) as well as network checks (dhcp client, ping). You can get them used from eBay for a bit more than a hundred bucks.

If you're doing a whole lab's worth of cable, this may be a worthwhile investment. Mine's been invaluable.


Try QCheck. It is free software for the windows platform. Or get LRAT 1000 from Fluke Networks for around £600

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