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I'm only getting 10 Mbps on my Ethernet connection but the NIC supports up to 100 Mbps. Could the Ethernet cable be the culprit? What labels on the Ethernet cable should I look for to make sure it's good enough?

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Steven, as it's been a few days, maybe now would be a good time to select an answer and close the question? The answer Troggy provided is accurate and consistent with troubleshooting techniques in the Telecom industry. – Everett Nov 22 '10 at 5:21
if your getting 10 Mbps why are you complaining? – user62794 Jan 12 '11 at 19:40
up vote 10 down vote accepted

For 100mb speeds, you will want to make sure you have at least "CAT 5" (Category 5) or better cable. "Cat 5e" and "Cat 6" would work as well.

As for your speed problems, your NIC in your computer needs to be 100 mbps capable. Your router or switch that it is connected to needs to be able to support 100 mbps speeds also. If these two are correct, you either have a poor or damaged cable or it could be the settings of the computers connected. Using too long of a cable would cause speeds to be limited also, but are you using cable runs longer than 100 meters?

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CAT5 cables are usually blue - see photo in - though I'm not sure this is any kind of standard. I'm also not sure that the device will actually recognise a too-low-CAT cable, or whether you'll just get more failures and retries. However, I suspect the ethernet driver (or firmware) may automatically switch to a lower speed if it recognises a high failure rate. – Steve314 Nov 19 '10 at 21:34
@Steve314 No, there is no standard for the color of the outer covering of network cables. They can be ordered in every color and various lengths. The different colored ones work great in a switch room where you have 100's of cables and colors make it easy to organize. As for what happens with lower rated cable or you use too long of a cable, the card will connect at the next lowest speed, which would be 10 mbps down from 100 mbps because the rated speed is unreliable (lost packets, time-outs, etc.). – Troggy Nov 19 '10 at 21:46

If you have a 100MB port you are plugging it into, try turning off "auto detection" for link speed on your computer, and see if you can force it to 100Mbs, some older equipment have issues with speed auto negotiation.

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You want CAT5e or CAT6 (supports Gigabit ethernet). I've had success using CAT5 on 100MBps networks. It is likely that the device you are connecting to doesn't support 100MBps speeds. If it does, you need to look in the configurations of both devices to find out what is limiting the speed.

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