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I want to use a crossover Ethernet cable to connect two computers directly for file transfer between the two. I have several Ethernet cables, but not sure if they are crossover? How to tell a Ethernet cable is conventional or crossover? Thanks and regards!

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I believe most UTP/RJ45 Ethernet interfaces nowadays are Auto-MDIX and therefore you may find that any Cat5/Cat6 Ethernet patch cable will work. Of course, this might apply only to switches and not to computer NICs - in which case all bets are off. –  RedGrittyBrick Feb 11 '11 at 15:55
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Look at the ends of the cable. If the color order is identical, then it is a patch cable (or as you said "conventional"). If the color orders are different, then it is a crossover. Also, keep in mind that USUALLY (not all the time) crossover cables are red. Obviously they can come in any color though.

Below you can see the colors of the twisted pair wires inside of the RJ-45 connector. For more information on this, or if you would like to know about the TIA/EIA-568-A or the TIA/EIA-568-B standards, please refer to this wiki page.

enter image description here

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See Network Cable Color Conventions for a discussion of jacket color. –  Dennis Williamson Feb 11 '11 at 15:49
    
Is this the answer you were looking for @Tim? If so, you can accept it by clicking the arrow to the left of my answer. –  David Feb 17 '11 at 16:15
    
@Tim. Is this the answer you were looking for? If so, you can accept it by clicking the arrow to the left of my answer –  David May 26 '11 at 15:18
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Most modern Ethernet equipment will auto-negotiate and doesn't care whether the cable is cross-over or not.

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This happens to be a requirement of Gigabit Ethernet. 100 Mbit will not do it though. –  Zan Lynx Feb 11 '11 at 17:23
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@Zan: Most modern 100BaseT equipment supports Auto-MDIX. It's specified, but optional, in GbE. –  Dennis Williamson Feb 11 '11 at 17:31
    
I'll try to find a reference source, but I am almost certain auto-MDIX is a requirement of the Gigabit Ethernet specification. I've used a lot of 100 Mbit equipment that will not work without the correct cable so I don't know about "most modern 100BaseT." –  Zan Lynx Feb 11 '11 at 18:23
    
Okay. It is optional, although I've never run into a system that didn't have it. See standards.ieee.org/getieee802/download/802.3-2008_section3.pdf section 40.4.4: "Implementation of an automatic MDI/MDI-X configuration is optional for 1000BASE-T devices." Sorry about that. My confusion. –  Zan Lynx Feb 11 '11 at 18:41
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Don't worry, most modern Ethernet cards support both modes and will automatically recognize type of the cable.

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