Crossover or Straight through?

The EIA/TIA puts the standards in UTP cable, and when cabling a network there are two standards. T568A and T568B these standards are important when deciding to put a crossover cable or straight through cable. This tutorial is going to be talking about when and where to apply these different standards.

We are going to be focusing on the UTP cable and with the RJ-45 connectors; in order for the communication to work properly we need to make sure we understand where to put these cables. Let’s first look at the RJ-45 connector, this connector has 8 pins and each copper wire.

Each pin in the Rj-45 connector does a different thing. Although not all pins or wires are used, they provide grounding along with helping the signal from becoming weak in the cable. So for the T568A standard the colors of the UTP as follows:

In Pin 1: Green/White (Striped Green)

In Pin 2: Green (Solid Green)

In Pin 3: Orange/White (Striped Orange)

In Pin 4: Blue (Solid Blue)

In Pin 5:  Blue/White (Striped Blue)

In Pin 6: Orange (Solid Orange)

In Pin 7: Brown/White (Striped Brown)

In Pin 8: Brown (Solid Brown)

For the standard T568B the colors are almost the same but with a few differences.

In Pin 1: Orange/White (Striped Orange)

In Pin 2: Orange (Solid Orange)

In Pin 3: Green/White (Striped Green)

In Pin 4: Blue (Solid Blue)

In Pin 5: Blue/White (Striped Blue)

In Pin 6: Green (Solid Green)

In Pin 7: Brown/White (Striped Brown)

In Pin 8: Brown (Solid Brown)

These standards are put together for one reason, to make the data or electic signal travel up to 100 meters. Now you could make your own standard and devices would be able to communicate but not has far and it may even cause transmission errors in the cable. Who knows? But for one thing it would make difficult for another person to learn your color code. So when setting up cable the first thing you need to choose is what standard to use. After you picked you standard can you just connect anything and everything with the same pin out? No!

One to remember is if it’s a like device now this is not always the case like a PC connected to a router would need a crossover but usually a PC to PC, or router to router, switch to switch these will always be a crossover cable. What is a crossover cable? The pins in a crossover cable are switched so one end will have the either T568A or T568B and you will change the pins on the other end. So for example if we had T568A on one end of the cable you could simply put T568B on the other end or vise versa. (That’s another reason they put standards in) 🙂

For Different devices like a PC to a switch, switch to a router, etc. Will usually have a straight through cable. Meaning the pins don’t change. If you have the same standard on one end of the cable keep it same on the other end. So for example if you had T568A on one side put T568A on the other side of the cable.

That’s that! The standards can get confusing if you over think them. There are other sites out there that go over why the different standards and why some devices send and receive on other pins. But the one thing to remember is that the colors don’t really mean anything as long has the pins or pairs match with the other end. Remember this depends on the type of cable, straight through will match the pairs/pins. Crossover will mix pins 1,2,3, and 6.

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