Network cables use a standard color scheme to maintain consistency around the world. In this video, you’ll learn about T568A and T568B color schemes for eight-conductor twisted pair cabling.
As you can imagine, the standardization for ethernet wiring is that extends well past the borders of any country. There’s an international standard managed by the ISO/IEC 11801 cabling standards document that defines the different classes of networking standards.
In the US, there’s the Telecommunications Industry Association, or TIA. This is a standards-based organization that has created a standard for the installation of cables in a commercial building. You can find this in the ANSI/TIA-568 standard. Inside of that standards document is the definition of what wires go on what pins with which connectors when you’re using an ethernet network. We refer to the standardization of the pins and the colors as the T568A color scheme and the T568B color scheme.
We need this set of standards so that we can walk into any building or look at any ethernet cable and see a consistent coloring of wires no matter where we go. This not only helps with the process of the initial cabling installation, but it also helps when troubleshooting that cable. These two standards of the T568A and T568B are both used on the same RJ45 type connection. But you can see that the colors used in each of these standards is slightly different from each other.
In the US, and probably in most places, you’ll find that the T568B standard is what is commonly used. It would be unusual for an organization to start with one standard and then change over to a different standard in the middle of their installation. Normally, organizations will be very consistent with their wiring standards. And once an organization starts using a particular standard, that’s the one they normally will stay with.
You also want to be careful about mixing and matching these. On a gigabit network, you would never put a T568A wiring scheme on one end of a cable and the T568B colors on the other end of the cable. You may even find references on the internet that tell you that this is a crossover cable with ethernet. But if you actually go through and look at the pinouts, you’ll see that that’s not actually the case. You would never want to mix 568A with 568B.
Understanding the color schemes is not only important for the A+ exam, it’s also important for any network that you walk into where you’ll need to perform some type of crimping or cable management. This is something where the T568A and T568B will certainly be used. But fortunately, there are a number of similarities between these two.
You can see on the T568A, pin 1 starts with white and green. Pin 2 is green. Then it moves to white and orange, blue, white and blue, orange, white and brown, and brown. Now, if you compare that to the T568B, there are similarities.
For example, you can see that the blue colors on pins 4 and 5 and the brown colors on pin 7 and 8 are exactly the same between them. That means you only have to memorize the differences between pins 1 and 2 and pins 3 and 6.
You should be able to pick up any ethernet cable, look at the cable, and be able to determine which color scheme was used for that particular cable. For example, we have an ethernet cable here. We flipped it over, and you can see that it’s white and orange and orange. It’s white and green and blue. It’s white and blue and green. And it’s white and brown and brown. And if we were to take our T568B color scheme and overlay it on the top of that cable, you can see that it matches perfectly. That means that this cable was crimped with the T568B color standard.
This is something that is very easy to get wrong if you’re crimping your own cables. These little wires can be difficult to manage, and they’re even more difficult when you slide them into the RJ45 connector just prior to crimping them down.
It’s often useful to put the wires into the RJ45 before crimping, and then to look at the wires, just like we did in the previous slide, to see if they were matching up exactly to where they should be. And if they’re not, we can pull the cable out, readjust, put it back in. And when we get it right, we can crimp those down.
Sometimes you’ll run into a jack like this one where you’re punching down the cables, and they’ve already told you what colors you should be using for each of these different connections. You can see that the A colors are along the top and the B colors are along the bottom.
You’ll also notice that this jack does not follow the same color scheme as the T568A or T568B. That’s because they put the color scheme here to make it easier for you to install. Inside the internals of this jack, it will be putting the correct pins in the correct place on the RJ45 connector itself.
Here’s another example with a different keystone jack. You can see that there are four wires that go on this side of the jack, and four wires on the other side of the jack.
This jack shows us if you’re using T568A, you would put a green, a white and green, a blue, and a white and blue into those four areas, and you would punch them down. If you’re using 568B, you would use orange, white and orange, and blue, and white and blue. And on the other side of the jack are the other four wires, and you would put them in with the same color scheme that’s specified for either T568A or T568B.