I was just making new short UTP cables, and I was happy that when I checked the cable through an Ethernet Cable Tester, all 8 wires were straight to each other and was perfect. When I plugged the UTP cable in the laptop, and plugged another end in the router, I was getting nothing, and then after some time, it started flashing. The lights stopped flashing, then started flashing, and then stopped, and it kept like that!

I am confused as to why is it doing so, after all, all 8 wires were straight connected to each other. It should work, but it's not working! Sometimes, it gets connected, but takes a lot of time, and the rest of the time, the lights flash, and then stop flashing (the lights in the ethernet port plug area)!

And it's a straight cable!

Can anyone help me out with this issue please?

Ethernet Cable Order:

Orange (White Stripe)
Green (White Stripe)
Blue (White Stripe)
Brown (White Stripe
  • Sounds like an intermittent connection. You likely will have to re-crimp one or both of the connectors.
    – Ron Trunk
    May 2, 2016 at 1:08
  • @RonTrunk : I am not surely getting can you explain please? I did multiple recramping and still it doesn't work???
    – Umair Shah
    May 2, 2016 at 1:10

2 Answers 2


There is a lot more to making a working UTP cable than just having eight wires connected straight through.

You must meet the required measurements, such as frequency, insertion loss, NEXT, PSNEXT, FEXT, ELFEXT, PSELFEXT, return loss, propagation delay, delay skew, balance, longitudinal conversion transfer loss, etc. Splitting pairs (you seem to do this correctly), untwisting too much at the terminator, exceeding the bend radius, etc. can all cause poor cable performance.

If this is horizontal cable, it needs to be <= 90 meters of solid-core cable with matching terminators. If it is a patch cable, it needs to be <= 5 meters, and it should be stranded cable, with matching terminators. The terminators must match the cable type (stranded or solid core) and be the same category as the cable.

The symptoms you describe usually happen with 1000BASE-T and poor cable that can't pass the test suite. If your company doesn't own the proper tester, it can rent one by the hour.

  • Respectfully, I would suggest that if you don't know that, your company should hire a cabling firm to do this for you.
    – Ron Maupin
    May 2, 2016 at 1:15
  • It's just 1 Meter cable so there is no length issue..!
    – Umair Shah
    May 2, 2016 at 1:15
  • Well I am trying to do this myself as I bought all the needed hardware so please if you would help..!
    – Umair Shah
    May 2, 2016 at 1:15
  • We can't teach you how to cable on this site. You can still hire someone to do it for you with your materials, assuming they are the correct materials. This is your business, so I think it would be foolish to not do it correctly.
    – Ron Maupin
    May 2, 2016 at 1:17
  • 1
    Unless you have the correct tester, you really won't know if it truly works or not. You may end up with a lot of damaged frames which cause retransmissions. This may not be evident up front, but your throughput will suffer.
    – Ron Maupin
    May 2, 2016 at 1:20

My bet would be on a poor connection. Crosstalk can sometimes be an issue with Ethernet but I very much doubt it would be a big problem on a link as short as 1m unless you have untwisted a crazy ammount of wire.

The things I would check.

  1. Make sure your materials are in-order. Is your cable proper copper or crappy CCA? Are your plugs designed for the type of cable you are fitting them to? I've learnt the hard way that using plugs designed for solid core cable on stranded core cable will result in very unreliable connections.
  2. Make sure the pins are being pushed in correctly, they should sit straight and just below the surface of the connector. If they are sticking out and/or sitting at an angle then the connector has failed to crimp properly.
  3. Make sure the cores are pushed fully home in the plug before crimping. Sometimes you have to pull the cable out and re-trim it if the cores don't want to site nicely.

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