Understanding Straight and Crossover Ethernet Cables

You may have heard the terms “straight” and “crossover” used to describe Ethernet cables. In order for your network to function correctly, it’s important to recognize the differences between one and the other. “Straight” is the term used to describe an Ethernet cable that will connect a PC to a switch or a hub. The ports on a PC and a switch are wired differently, and a straight cable makes sure that the transmit wires on one connect to the receive wires on the other – simple enough. There’s nothing too fancy about a straight cable, but being able to identify one is important. Basically, when if you flip both ends of a cable upside down (with the clip facing the floor) and look at the ends side-by-side, the colored wires should be in precisely the same order on both ends. If you’re worried about the colors, we’ll get to that in a future article.

Where a straight cable is used to connect different types of ports, a crossover cable is used to connect ports of the same type. For example, if you wanted to connect two PCs directly to one another (without a switch or hub), a crossover cable would be used. The wires in a crossover cable are literally “crossed” so that the transmit wires on one device will now connect to the receive wires on the same type of device. So, any time that you want to connect devices of the same type, use a crossover cable. Note that switches and hubs use the same type of port, so when connecting a PC to a PC, a switch to a switch, or a switch to a hub, always use a crossover cable. Unless…

Right. There’s always an exception. If you’ve ever looked at a hub or switch, you may have noticed a port marked with an X that includes a little button or switch next to it that can be turned on or off. This is an “uplink” port, and is used to connect to another switch or hub. The uplink port is a special port that contains a built-in crossover capability, basically allowing you to either use a crossover cable to connect to another switch or hub, or a straight cable. If the crossover button is “on”, then you could use a straight cable to connect the hub or switch to another hub or switch. If switched “off”, a crossover cable would be used instead.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of 2000Trainers.com. He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.