Ethernet is one of the most common types of cables, used to connect devices like computers and routers to the Internet. The end of an ethernet cable, an RJ45 connector, looks similar to the end of a phone cable, an RJ12, but bigger. While phone cables have four to six wires on the inside, ethernet cables use eight. Ethernet cables come in both solid and stranded variants.

Ethernet Categories

There are a few different variations of ethernet, the foremost being the cable category. This type of cable is abbreviated as “Cat#”, with higher numbers being newer versions of ethernet capable of faster signal speeds. These categories are defined by the Institute of Electrical and Electronic Engineers (IEEE).

Cat5e

Cat5e is an upgraded version of the original Cat5 cable and the current standard version of ethernet. It is capable of data speeds up to 1 Gbps (gigabyte per second) with a bandwidth of 350 MHz (MegaHertz).

Cat6

Cat6 is the next step up and will become the new standard once Cat5e is inevitably phased out. These can support speeds up to 10 Gbps, ten times faster than Cat5e, with bandwidth of 550 MHz. Currently, this level of speed is overkill for at-home use. They are more common in facilities setting up basic networks, like small businesses or schools.

Cat6a

Cat6a (“a” meaning “augmented”) have the same 10 Gbps maximum speed as Cat6 but better overall performance, including a 750 Mhz bandwidth. These cables are thicker and better shielded, reducing signal interference and allowing them to retain high signal speed over longer distances. The downside is that the increased thickness gives them less flexibility.

Cat7

Cat7 is shielded by default and capable of speeds of 100 Gbps at lengths under 15 meters (roughly 49 feet). Beyond that length, they revert to the same 10 Gbps speed of Cat6 and Cat6a. Their bandwidth rolls in at 850 MHz, superior to any previous version of ethernet.

Cat8

Cat8 is the latest and greatest version of ethernet but is still too new to have seen widespread use just yet. It can support speeds of 30 Gpbs with 2000 MHz (2 GHz) bandwidth, but will only work for up to 30 meters. Presently, Cat8 is mainly used for short runs in data centers with servers and similar equipment.


It should be noted that simply switching out your ethernet cable for a higher category will not necessarily make your Internet faster. For example, if the Internet speed you are paying for is less than 1 Gbps while you are using Cat5e, upgrading to Cat6 will not make your Internet any faster. However, say you are using a Cat5e cable and are paying for 5 Gbps. In that case, upgrading to Cat6 would drastically improve your Internet connection. Ethernet cables are backwards compatible as well. You could use something like a Cat6 cable on a Cat5e connection, but you will only get speeds up to the limits of the weakest link in your set-up.

Users will also need to remember that the numbers listed are the maximum speeds the cables are theoretically capable of. Even if your service provider advertises gigabit Internet, the times when you actually get those speeds are probably going to be few and far between. Signal strength also decreases as the cable gets longer since it has to travel further. A 5’ cable will always be faster than a 100’ version of that same cable. For any category (other than Cat8), a single ethernet cable has a maximum length of 100 meters (328 feet).

Ethernet Shielding

The next factor is whether an ethernet cable is shielded. Electrical interference is one of the main causes of signal loss and can be a big issue with unshielded cables. Like with ethernet categories, there are a few different options here.

Twisted Pair (TP)

Twisted pair (TP) refers to the eight wires inside the cable being twisted together. This is an industry standard and all other designations covered in this section stem from TP.

Unshielded Twisted Pair (UTP)

Unshielded twisted pair (UTP) is, as the name implies, unshielded. The lack of shielding makes these cables less expensive and more flexible. On the downside, signal quality will not be as good and there is a higher chance of signal interference.

Shielded Twisted Pair (STP)

Shielded twisted pairs (STP, sometimes SSTP) are protected with a braided shielding between the outside jacket and wires inside. The shields are made of copper or a similar conductive material. This shielding reduces signal interference, improving the overall quality of your connection.

Foiled Twisted Pair (FTP)

Foil twisted pairs (FTP, or SFTP) have the same function as STP but use shielding made of foil.


Unshielded Twisted Pair vs. Shielded Twisted Pair cables

A UTP cable (left) vs. an STP cable (right)

Ethernet Connectors

Every ethernet cable has a connector on either end that looks similar to a phone cord connector. These plastic pieces at the end of the cable are called RJ45 connectors. While similar to a phone line, they are a bit bigger. Each RJ45 has eight metal contacts, one for each of the wires inside the ethernet cable.

RJ45 Connectors

While RJ45 connectors are all fairly similar, there are several different varieties. Some connectors will only work with solid cable, some only with stranded, and others work with both. If you are making a shielded cable, you need to make sure the RJ45 connectors are also shielded. Size can also be an issue in more ways than one. Ethernet cables are manufactured in multiple AWGs (American Wire Gauges), so trying something like a Cat6 connector with Cat5e cabling may not work. The connector itself might also be shaped differently for newer cables like Cat6a and Cat7, requiring a different crimping tool than usual.

As far as installation goes, preparing an ethernet cable is not too different from other types of wire. You will need the cable and connectors as well as a stripper, crimp tool, and scissors. Having a tester to make sure your new cables are working is usually a good idea as well.

Ethernet Pinout

The arrangement of the wires inside an ethernet cable is crucial during installation. The wiring scheme showing how the wires are connected to the contacts is called the pinout. Different equipment can need different RJ45 pinouts, but there are a few main industry standards. Other pinouts besides these standards do exist so users may need to dig around a little to find the pinout for oddball equipment.

Straight

A straight pinout uses the same wire configuration on both connectors. This is your standard off-the-shelf cable used for common applications like connecting your computer to the Internet. If you numbered the pins 1-8, pin 1 on side A would connect to pin 1 on side B. Then 2 to 2, 3 to 3, and so on.

There are two different variations for the straight pinout: T-568A and T-568B. They use different color coding when connecting the wires to the contacts, but this is not the only difference. T-568B is the newer and more common of the two, matching the old 258A color scheme AT&T used to use. While T-568A is not necessarily worse, these two pinouts are not compatible with each other. Make sure you are only using one or the other throughout your network.

T-568A pinout and T-568B pinout, straight pinout
Straight-thru ethernet cable

T-568A (left) vs. T-568B (right)

Note how the green and orange pairs swap places from one pinout to the other.

Crossover

A crossover cable uses two different pinouts on either end of the cable. This allows two computers to talk to each other directly through the ethernet connection. If you try to use a straight pinout cable the same way both computers will be trying to talk and listen to each other at the same time, so nothing will happen. The direct connection of a crossover cable eliminates the need for middleman equipment like a hub.

Crossover with T-568B and T-568A

A common crossover cable, using T-568B on side one and T-568A on side two.