Structured Cabling (Wiring)

Structured Cabling consists on a laying of cables inside a building with the intention of implanting a local area network (LAN). It use to be a twisted pair of copper, for networks of type IEEE 802.3. Nevertheless, it could be optical fiber or coaxial cable, too.


The cabling standards used in computer networks are the T568-A and T568-B. The correspondence between the pins and wire colors for each standard is as follows:

End   T568-B	End   T568-A
Pin 1 White/Orange	Pin 1 White/Green
Pin 2 Orange	Pin 2 Green
Pin 3 White/Green	Pin 3 White/Orange
Pin 4 Blue	Pin 4 Blue
Pin 5 White/Blue	Pin 5 White/Blue
Pin 6 Green	Pin 6 Orange
Pin 7 White/Brown	Pin 7 White/Brown
Pin 8 Brown	Pin 8 Brown

Straight-Through Wire

A straight cable has the same standard at both ends, this type of wire is used for connecting  devices  in different  layer of OSI model. A cable with only one standard at both ends (T568A or T568B) will be linear or direct.

 Example:

 - From PC to Switch / Hub.
 - From Switch to Router.

Crossover Wire

A crossover cable has a different standard at the ends (one end  T568B and the other one T568A). This is for connecting devices on the same layer of the OSI model.

 Example:

 - From PC to PC.

 - From Switch / Hub to Switch / Hub.

 - From Router to Router (serial cable is considered  a crossover one.)

There is also a type of wire called Rollover or Mirror Wire, that is used to connect devices to the console ports of a router or a switch. It is simpler than it seems, because you can just choose a standard to do, 568A or 568B, make an end (of  wire)  in the normal way and the left one will be done inverse. For example, if the last color from one end was Brown, then Brown will be the first in the other one and so on.

To see the Spanish version of the article, click here.