I had a naff batch of cat5 connectors (the latching mechanism didn't work) so decided to order in some cat6 connectors in preparation for the inevitable upgrade.

My existing reel of for making patch cables is cat5e utp stranded. I made up a few cables and tested them- none of them worked. I recrimped and still nothing. When i check them with a multi-meter not all pins are connected.

This reel has always worked with the previous cat5 connectors so I tested the cat6 connectors on a reel of solid cat5e cable and they work fine.

Any ideas what I might be doing wrong? Or what might be at fault? (cable/connectors) and how I can diagnose?



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    This doesn't really answer your question, but making your own cables is likely a waste of time/money. See here for a nice explanation: everythingsysadmin.com/2011/01/… – ThatGraemeGuy Jan 16 '12 at 10:31
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    isn't cat6 grounded using the braid around the cable pairs ? – Sirex Jan 16 '12 at 10:37
  • What's the difference between a CAT5 connector and a CAT6 connector, other than the label on the package? CAT6 uses the same 8P8C connector that CAT5 does as far as I know. In addition, what inevitable upgrade are you referring to? GbE will run just fine on CAT5 and CAT5e cable. Are you upgrading to 10GbE? – joeqwerty Jan 16 '12 at 11:40
  • cat5 connectors are a single piece (the cores are all aligned in a single horizontal line). cat6 connectors come as two pieces- a guide rail which you load the 8 cores into before loading into the outer shell and crimping (the cores are aligned in 2 rows of 4) – Lee Tickett Jan 16 '12 at 11:45
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    Do you have mismatched stranded vs solid cable and connectors? – Keith Stokes Jan 16 '12 at 13:25

I've hand-crimped hundreds, maybe thousands of patch cables. The thing that normally bites you is trying to use modular plugs designed for stranded wire on solid conductor cable or vise versa. They have to match. If not, you'll get enough connectivity for a DVM to show that your pinouts are correct, but not enough to support a 100Mhz signal.


While the cables and connectors look very similar, there's a difference. Category 6 uses thicker 22 AWG wire, while Category 5 uses thinner 24 or 26 AWG wire. This causes two different problems:

The smaller wire pairs (CAT5) aren't large enough to securely fit in the connectors made for the larger wire pairs (CAT6). You can tell a CAT6 connector (on the left in the below image) by the fact that the wires are staggered at the end of the connector, so that 4 pairs of larger wires will fit.

CAT6 and CAT5 comparison

The second issue is that the conductors in CAT5 RJ45 ends are generally not strong enough to pierce the thicker insulation as well as the thicker wire in CAT6 cables. So even if you can physically fit the cables, you won't get a quality connection.

  • Is the left one the CAT6? – Lucas Gallindo Sep 9 '16 at 14:09
  • Yes, the left one is CAT6. Also, this answer is the opposite. The question is asking why CAT5 cables don't work with CAT6 connectors. – Sawtaytoes Dec 22 '19 at 2:17

Cat6 has larger diameter individual conductors as opposed to cat5. You are using cat6 connectors on the smaller diameter cat5. That is most likely your issue. Tolerances on the rj45 connectors are very marginal. If they were compatable with every kind of cable they wouldnt sell different connectors for specific cables. My guess is you got a lucky crimp on a solid cat5 cable. I have heard of people doing this to cut costs. The bottom line is if you want cables with quality connections you cant cut corners and mismatch connectors.


Cat5 and Cat6 have different AWG specs. While they -can- overlap in size, their specs allow different ranges, causing one scenario of "It worked before, why not now."

Cat5e: 24-26 AWG Cat6: 22-24 AWG

The other side of this is the difference between RJ45 connectors intended for Solid wire vs connectors intended for Stranded wire.

Solid: The 8 crimp pins have fangs that are aligned down the center of each pin. Stranded: The 8 crimp pins stagger their fangs left and right, as to bite more conductive surface and more of the individual conductive strands.

Another side note on stranded vs solid wire:

Stranded wire tends to break little strands easily, though they -usually- squeeze against the other non-shielded strands and continue to make -a- connection, their impedance changes a very tiny amount per break. In total, folding a stranded wire repeatedly continuously degrades the connection with each little break, but a solid core exhibits catastrophic failure as one break is a complete break of the conductor.

High flexibility and high trampling applications benefit from stranded wire. High precision applications, such as very long runs and very high speeds, benefit from solid core wire.


Compared with Cat 5 and Cat 5e, Cat 6 has more stringent specifications for crosstalk and system noise. Additionally, stranded cable has higher attenuation than solid cable. In my opinion, this is what bit you, assuming that you've ordered connectors that are compatible to stranded cable (and not to solid cable), which would've been my first guess otherwise.


So it turns out that cat6 connectors are not neccessarily backwards compatible with cat5(e) cable. I'm struggling to find sources to cite at the moment- http://www.cat6.com/faqs/freqAskQues%20cabling%20system.aspx for example suggests they are backward compatible- lots of confusion!


The company we used told me a story of a job they did when they first started using a new set of Cat6 clip-shut terminals. They had connected 1000's of cables to a giant patch panel and they all failed because the clippers they had used did not clip the ends of the cables precisely flush and so 1mm of cable was poking out and when the metal terminal was clipped shut, all the cables touched the metal case and so shorted.

Once they worked out the problem it was simply a matter of getting some better clippers and clipping the 1000's of cables exactly flush and they all worked a treat.


I've been researching this myself too. What I know now is this:

Beside the size difference in diameter between CAT5 and CAT6 cables, the other major difference is SOLID core versus STRANDED cores. For stranded core cables, the teeth on the pins are made to sink into the individual wires (you'll see some labelled as 2-pole or 3-pole to describe the number of teeth on a pin); whereas for solid core cables, the pins are a little longer (deeper) and are designed to straddle (or grab or pinch) the solid copper wire from both sides, in order to make contact with it.

Also not all CAT6 plugs come in 2 pieces. Some come in one and some also come I 3 pieces. That's just a matter of preference and made to make it easy for guiding the wires into the plug.

When buying plugs, also pay attention to the thickness of the gold plating. Cheap indoor plugs only come with 6 micron, good ones will have 50 microns.

Finally, there are TWO major manufacturers that make these plugs: commonly WE/SS Stewards, or the Tycon Electric AMP styles. Each have their own crimper dyes. TE AMP ones have pins that are a little closer to each other than the Western Electic ones. So if you use the wrong tool, you'll end up buggering up the plug.

And, all these come for shielded or unshielded cables... Shielded plugs have a metal wrap around them.

There, now you know.


I faced the same problem as yours, but when I got solution then I came to know 'how stupid am I'.

The solution is 568-B Wiring on both ends. This applies to Cat6 as well. Check out the article How to Make a Category 5 / Cat 5E Patch Cable.

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