The modular plugs or what I like to call "end-caps" for Cat6 cable, I have the kind where you can push the cable all the way through then cut so you know you have proper cable alignment. I thought this would be the best way to go so I don't have to dreadfully stare at the modular plug to determine if the wiring is in the right order.

Well, what I have noticed is that it is impossible for me to cut the wiring back far enough which creates excessive amount of "noise" and crosstalk and is just a bigger issue than what I imagined. Am I doing something incorrectly or is this just a hazard of using this type modular connector?

Below are images of my crimp work - looks good to me, but the cable is still not functioning!

Image 1

Image 2

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    It's much easier (and cheaper) for the novice user to buy pre-made patch cables rather than make them. If you have unterminated cable (e.g., run through a wall) get a punch down keystone jack or patch panel to terminate the ends; don't crimp on an RJ-45 jack
    – mmathis
    Commented Mar 6, 2017 at 16:35
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    Don't rush into wasting more money without first posting pictures. And taking mmathis's advice if it applies. If you don't know what's wrong with the type of wirecutter, you won't know what's a better one to buy, for instance. A better quality of the wrong type may be a great cutter that's of no benefit to your problem...
    – Ecnerwal
    Commented Mar 6, 2017 at 16:43
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    @BellHopByDayAmetuerCoderByNigh See a previous answer of mine: diy.stackexchange.com/questions/107401/… for a schematic of how home network wiring is typically done. If I understand you correctly, you'll have 4 connections going from the switch - one to each room - this could be a patch panel, and they make small panels. Though, again, the mantra is buy bigger than you need now, so even a 12-port patch panel would be a good choice (and they're only ~$15 or so)
    – mmathis
    Commented Mar 6, 2017 at 16:47
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    The "proper" way is to put a keystone jack in a wall plate in the room, and a keystone jack or patch panel at the central location where all the cables terminate. You then can use short pre-made patch cables to connect from the jack to your switch/router/PC/etc.
    – gregmac
    Commented Mar 6, 2017 at 16:47
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    @BellHopByDayAmetuerCoderByNigh You've cut the jacket too far back, and untwisted too much length of the wires. The jacket should extend underneath the crimped portion of the RJ-45 plug, and the wires should remain twisted as much as possible - no more than about 1/2" should be untwisted - and most of that is inside the "channels" at the end of the jack. Cat6 is far less tolerant of this than cat5e.
    – mmathis
    Commented Mar 13, 2017 at 18:16

3 Answers 3


Pin 6 is not crimped. Your crimp die is defective or you need to try again.

All the pins should be at the same level.

not a good crimp

But really, punch-down into jacks and buy patch cables as already suggested. Cheaper and more reliable.

  • Ugh - brand new crimping tool. Must be why it was only $30. I'll try to re-crimp and if that does not work will put on a new "end cap" Commented Mar 8, 2017 at 14:11

When you're learning to crimping these, you really need to have a cable tester.

Generic Cat5 cable tester

These plug into both ends and cycle through each conductor, showing you if there are any disconnected or miswired.

Tester in action

Once you identify the problem you can fix it. Be prepared to cut off and redo connectors a few times while learning.

  • Good recommend, I will def invest in one of these. I will say that atm, for every 12 modular connectors I add, only 1 cable is good (so 2/12 are good) Commented Mar 7, 2017 at 20:42
  • Well there are two connectors on every cable, and in each of those, 4 conductors that are critical to ethernet (orange and green pairs): all it takes is for one pin on one connector to be broken and the cable "won't work". (FYI the other two pairs -- blue and brown -- are used for gigabit and PoE; for analog phone, only the blue pair is used)
    – gregmac
    Commented Mar 7, 2017 at 20:53
  • Interesting to know, I had no idea that blue & brown pairs were used for that. Commented Mar 7, 2017 at 20:56
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    Gigabit is the basic ethernet of today - 10 and 100 are legacy, and Cat6 speaks of a thought of going to 10 Gig (though 6A is preferable.) So all wires are used in the current standards as applicable to most equipment for sale in 2017. The tester pictured only shows connectivity, not the qualifications needed for a 10-gig Cat6 install. Those testers cost much more. Also pin6 is clearly (at full size) not properly crimped on the first picture.
    – Ecnerwal
    Commented Mar 7, 2017 at 22:34

Your key problem is that pin 6 is not crimped. Today's switches use auto-negotiation to determine speed (10/100/1000) and half or full duplex. Without pin six the switch can't negotiate and the link will not come up. Look up on the ol' interweb and search for quality features to look for in a crimper and invest in a good crimper.

  • 4
    How does this differ from the accepted answer?
    – Machavity
    Commented Mar 13, 2017 at 17:47

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