What is a Crossover Cable?

David White

A crossover cable might sound like a thing of the past, but it is still in use today in various capacities. It's a cable used to connect two computers together for the purpose of direct communication. Another name for this type of cable is a null modem.

Problems connecting computers via crossover cable may use a cable tester for troubleshooting.
Problems connecting computers via crossover cable may use a cable tester for troubleshooting.

A computer user might want to test the behavior of one computer by connecting it to another, or to connect two computers to avoid having to buy a hub. Computers can also be connected so that two people can compete against each other in a multiplayer game. In each of these instances, a crossover cable can be used to make the connection.

Crossover cables negate the need for network hardware.
Crossover cables negate the need for network hardware.

For the first two instances, the computer user will want to make sure that the two computers are in the same workgroup. If they are not, then they will not be able to “see” each other. Once they are members of the same workgroup, the data transfer or monitoring can begin. This is sometimes a requirement for multiplayer gaming as well, so it's best for the user to check the protocols for both the game and the cable to be sure.

Many network cards have the functions inherent to a crossover cable built in. In this case, the user does not need to connect the computers directly as long as both are on the same network, primarily using the same modem or router. The network card does the work that would normally be done by the cable.

Computer users can buy a crossover cable at most computer stores and online computer equipment vendors, although they can also be made from commonly available materials. A number of do-it-yourself websites explain how they are made. People who want to make their own should remember that the signal pins that receive on one end are connected to the pins that transmit on the other. This is different from straight-through cable, in which the pins are connected like to like.

A crossover cable can also be used to connect two Ethernet devices. These devices can be single computers or networks. The principle is the same, but the connection speed and scheme are different, as is the purpose of the connection. In all cases, however, the data send and receive functions are crossed over at both ends of the cable, enabling full data transfer between computers, routers, and even networks.

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Discussion Comments

anon151523

I disagree. Cross-over cabling is a thing of the past unless you use very old hardware. There is no such requirement anymore as NIC cards will negotiate automatically.

anon123269

I agree with the post above mine. I was researching on the difference between a crossover cable and a straight through. Other explanations are way too technical, this is just about right. I'm not really tech savvy and when I read on other sites I have to read it twice or thrice. With this I just read through it once and understood it easily. good job!

anon93936

That feature is called Auto-MDIX.

anon63339

Second paragraph mentions that some NICs have the same functions as a crossover cable. What is the feature called? Please elaborate. Thanks!

anon62863

Thanks for this, was looking for a 'dummies' explanation and this was great to help wrap my brain around some networking concepts.

anon392

Short & sweet & understandable & excellent

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