A network card may have several types of connectors, with the most common being an RJ45 connector and a BNC connector (coaxial cable). In this article, we talk about the RJ45 ethernet crossover cable, as it is the most widely used.
What are the wiring standards?
There are two wiring standards that differ in the position of the orange and green pairs, defined by the Electronic Industry Association/Telecommunications Industry Association. The cables used are called twisted pairs, as they are made up of four pairs of wires braided together. Each pair of wires is made up of a solid-colored wire and a wire marked with stripes of that same color. It is highly recommended to use a category 5 cable between 3 and 90 meters long.
Why use a patch cable?
RJ45 is normally used to connect computers by a hub (a distribution box into which the RJ45 cables from the local area network computers are connected) or a switch.
When a computer is connected to a hub or switch, the cable used is called a patch cable, which means that a wire linked to plug 1 on one end is linked to plug 1 on the other end. The standard for making patch cables is >TIA/EIA T568A. However, there are also TIA/EIA T568B patch cables (the only difference is the colors of some of the wires, which does not affect the proper functioning of the connection, as long as the wires are joined the same way).
Why use a crossover cable?
A hub is very useful for connecting many computers and, overall, is faster than a coaxial cable connection. Nevertheless, to connect two machines, there is a way to avoid using a hub.
It involves using a crossover cable (also called a cross cable), with two wires crossing over one another. The recommended standard for this cable type is TIA/EIA T568A for one of the ends, and TIA/EIA T568B for the other. Of course, this kind of cable can be purchased, but it is very easy to make on one's own.
How to make an RJ45 crossover cable?
To make an RJ45 cable, buy a patch cable, split it in the middle, and then reconnect the wires using the following RJ45 color code:
|End 1||End 2|
|Not used||4||Blue||Not used||4||Blue|
|Not used||5||White/Blue||Not used||5||White/Blue|
|Not used||7||White/Brown:||Not used||7||White/Brown:|
|Not used||8||Brown||Not used||8||Brown|
||The ground strap is not crossed, so you don't have to split it.|