# New Cat6 Cable will only run at 10mbps



## PockyBum522 (Jan 25, 2008)

I just ran some brand new Cat6 cable and it will only work if I tell my NIC to force 10mbps.

The cable run is no more than 40 feet
The ends are untwisted the absolute minimum distance (Less than .5in)
My cable tester says there are no shorts/opens
When I try to use it at 100mpbs windows can tell the cable is plugged in, but it takes forever before it gives up and assigns some random private address.

I know the computer and router are not the problem. It's the cable. Any ideas?


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## Cellus (Aug 31, 2006)

If it has been working at 10mbps and not 100mbps, chances of it being a cable problem aren't all that high. This sort of behaviour is, quite frankly, weird. There really isn't much difference in the transmission behaviour of 10BaseT and 100BaseTX except for the "clocking", which in a nutshell simply transmits bits 10x more often. And a CAT6 cable would definitely be able to handle 100mbps. In Layman's, the rate should be auto-sensing between the interfaces - in brief Technobabble, the "timing" bits transmitted through the physical medium should be telling an aware interface what speed it is capable of ("Does it tap as fast as 10mbps or 100mbps? Am I hearing 100mbps?") and the signaling algorithm is pretty much the same.

While not impossible, the chances of the physical medium itself (in this case the cable) being the culprit is very low. Even if the cable did not meet CAT6 standards (and, say, fell short to CAT5/5e), it should still work. If it is only sensing 10mbps, then it means either the NIC or router is failing to properly detect/support/"trust" (read: stable connection) of 100mbps.

Does this problem also occur with another cable?


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## PockyBum522 (Jan 25, 2008)

Well it does auto detect and try to run at 100mbps, it just won't work. I had to force it to try 10mbps before I got anything. 

I tried a known good cable and it works fine, that's how I know the computer and the router are not causing it.

I did find one thing doing some research though. It appears cat6 needs special connectors due to a wiring size difference, and I was using older ones. I ordered some new ones and I'll try those. Have you ever heard of that causing problems? I'm a bit skeptical as my tester says the cable is fine, but I'm willing to try anything at this point since half my home network is down due to this.


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## Cellus (Aug 31, 2006)

Actually if the cable is following the proper CAT6 standards, it should be using RJ45/8P8C connectors (CAT5/5e uses RJ45/8P8C connectors also) and should fit into a standard RJ45 port. The connectors themselves may be of a higher grade, but it should still "fit" the port.

What brand is this cable? Did you buy it premade or did you crimp it yourself?


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## PockyBum522 (Jan 25, 2008)

I crimped it myself. The old ends fit into the jacks fine, but that's not the problem.


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## johnwill (Sep 26, 2002)

Sorry to say whenever I've encountered this issue, it's been mis-wired or poor connections.

I suggest removing the connectors and doing the job again.


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## PockyBum522 (Jan 25, 2008)

Okay, thanks. I'll let you know how it goes. I'm glad someone's encountered this before.


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## johnwill (Sep 26, 2002)

Make sure the cables are wired EXACTLY as follows: You want the 586-B configuration.

CAT5 Cable Wiring Diagram

HOW TO MAKE YOUR OWN CAT 5, TWISTED-PAIR NETWORK CABLES


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