Sometimes, you need to plug two computers into your network. If you’ve only got one ethernet cord or one free ethernet port, however, you’ll run into trouble. Some people might be tempted to try and split the ethernet cable in two. By cutting into your cable, splitting the wires, and attaching a new connector to each end, you can turn a standard 8-pin ethernet cable into two 4-pin ones. It’s a lot of work and you’ll need some new RJ45 connectors, but you’ll be able to use your single ethernet cord to provide internet to two computers. It will also mean that you only need a single ethernet wall port.
Unfortunately, this solution is not very good. While making an ethernet cord with two connectors at each end has some novelty value, the end result will be an unreliable cable that delivers slow internet. Here’s a comprehensive rundown of everything you need to know regarding splitting ethernet cables, why it works, and why it’s a terrible idea.
Why Split Cables?
Frankly, there aren’t a lot of reasons why you’d want to split an ethernet cable. If you think it’s a fun project, there’s nothing wrong with producing a 4-headed ethernet cord, but beyond that, you’ll almost always have access to a better alternative.
The only good use case for a split cable is in a situation where you need to connect two computers to a network and you’ve only got a single cable, but you also can’t move the computers close enough to the network device that you can cut the cable in half.
In order for splitting the cable to make sense, your need must be urgent, you can’t require a high-speed connection to the network, and you need to be in an extraordinarily odd situation where you have access to two new RJ45 connectors, you can’t buy a second cable, and you don’t have any unused cable available for the project.
This situation is very unlikely. Most people with RJ45 connectors just lying around also have boxes of literally hundreds of feet of bulk cable lying around. The primary use of these connectors is to transform giant spools or boxes of bulk cable into usable patch cables.
This means that if you have these connectors, you probably have lots and lots of cable that you can use to make long ethernet cables. If you don’t have the connectors, you’ll need to buy them, which involves a trip to the store or ordering them online.
If you can do that, you can buy a second ethernet cable, a switch, or another networking device that will allow you to connect your two devices to your network in a way that makes sense. Even if you somehow have connectors but no cable, a split ethernet cable is still a temporary solution that will only allow slow browsing. This means that you’ll inevitably end up replacing this split cable in a few days.
About Making Ethernet Cables
In the professional IT world, ethernet cable tends to be sold by the spool. These big spools (or boxes) of cable don’t have anything at either end. Instead, technicians cut the cable into short lengths and then painstakingly attach plastic RJ45 connectors to both ends. These connectors hold the wires inside the cable in a configuration that allows networking devices to make electrical contact with each wire, enabling the cables to be used for transmission.
The upside of this is that RJ45 connectors (the plastic doohickeys at the ends of an ethernet cable) are cheap and readily available. There’s lots of documentation on how to cut into a cable, arrange the wires, and attach the connector.
Category 6 (Cat6) cabling is currently the most widely installed wiring for ethernet. Some higher end installs are now using Category 6a (Cat6a) which offer better interference protection. Older installs commonly used Category 5e (Cat5e). Regardless of which type of cable is used the RJ45 connector works the same way and also uses the same pin configuration.
Try Cutting The Cable In Half
We’ll go over a plethora of downsides to making a split ethernet cable with two 4-pin connectors at each end in a moment. Before we do that, however, it’s worth noting that if you do happen to have two RJ45 connectors and you need to connect two devices to a network, you can simply cut the cable in half and make two normal ethernet cables.
This process is much easier than making a split cable and you’ll come out with two totally normal, perfectly useable ethernet cables at the end. Not only will your cables last for much longer, but you’ll also get normal internet speeds.
The only downside to this solution is that your cables will each be half the length of your initial cable, but that’s a very fair price to pay for dodging all of the issues involved with splitting an ethernet cable. Additionally, splitting a cable can reduce the length of your cable by a fairly large amount anyway, so this isn’t a downside in practice.
To make two 8-pin cables from an ethernet cable, cut the cable in half around the middle. Strip the plastic wrapping from the last couple of inches of wiring, carefully cut the cross connector, and untwist the internal wires.
Flatten them out and arrange them in the correct order (with the clip facing away from you and the wires pointing up, you want white/orange, orange, white/green, blue, white/blue, green, white/brown, brown), clip the ends so they’re even, and stick them in the connector. Then, carefully crimp the connector to hold the wires in place. Repeat this for each end of the cable and you’re done!
If you don’t have a crimping tool, we’ll discuss some ways you can go about the crimping process when we talk about making split cables.
Making Two 4-pin Cables
In order to get a high-speed internet connection, your devices and networking equipment use all 8 wires inside of an ethernet cord. The ethernet standard doesn’t actually require all 8 wires, however. It’s possible to get a slow connection out of a cable with only 4 wires.
This cable will be limited to speeds of 100 Mbps, or one-tenth of the speed of a cheap 8-wire ethernet cable. In theory, 100 Mbps is enough to watch videos in high definition under the right circumstances, but the actual maximum speed of the cable is low enough that you’ll run into problems in practice.
The 100 Mbps ethernet standard only uses 4 wires connected to pins 1,2,3,6. This means that theoretically you could then you the other 4 wires to connect to these 4 pins in a second RJ45 connector.
The more modern gigabit ethernet standard needs all 8 wires connected to function. This is why splitting the cable will make your network 10 times slower.
In order to split your ethernet cable to provide internet for two devices, you’ll need to split both ends of the cable. Splitting only one end will confuse your network and prevent the cable from working. Ideally, you’ll have four fresh connectors you can use, allowing you to replace any existing connectors on either end, but you can also very carefully cut the correct wires and splice them onto a new connector if you’ve got a lot of patience.
To make two 4-pin cables, you’ll need to separate the wiring inside of an ethernet cable at each end. One pair of connectors will be wired in the following order: white/orange, orange, white/green, empty pin, empty pin, green, empty pin, empty pin. The other pair of connectors will be wired in the order white/brown, brown, white/blue, empty pin, empty pin, blue. empty pin, empty pin.
Before you connect your RJ45 connectors, however, you’ll want to consider how RJ45 connectors actually work. There are two different elements in a connector that a crimping tool interfaces with. One element has a clip that presses into the outer shell of the ethernet cable, holding the connector in place. The other element pushes down small metal blades, causing them to pierce the wires inside of the connector and bridge a connection to the end of the connector.
The important thing to realize here is that the clip that connects to the outer shell won’t work properly if you split a cable. You’ll have to find an extra cable to cannibalize to provide the outer sheathe for both sets of clips, for one, and the cannibalized sheathe won’t actually be attached to anything. This means that the connectors will be liable to fall off.
Additionally, the X-shaped separator inside most ethernet cables provides extra stiffness and support, improving the efficacy of the clip on the connector. Since you’ll have to strip out wires fairly far down the cable to make a double-headed split ethernet cable, you’ll probably have removed this, making the connectors even flimsier.
Here’s a quick rundown on the full process involved in making a double-ended split ethernet cable
- Cut off the existing connectors at both ends. As mentioned above, if you really want to preserve the connector at one end, you can carefully do cable surgery and cut the wires you need for the other head and connect them to another connector. This is a LOT of work, however.
- Estimate how much space you’ll need between your two devices. Strip off the outer sheath from the ethernet cable far enough down that you can separate the wires with enough room to plug in both devices. Keep the sheath intact, though, as you’ll need it for later.
- Untwist the wires. Untwist all the way down to where you’ll need to separate them.
- Bunch the wires according to the wiring order above and split them
- At each end, fully untwist the wires, arrange them in the correct order, and cut across to square the ends.
- For each section of cable, slide on a section of cable sheath so your connectors have something to clip on. This means that you’ll have to either dramatically shorten your existing cable or have an extra cable that you can pillage sheath from, which means you could have just used the other cable.
- Carefully thread the wires into the connectors in the order above.
- Crimp on the connectors. If you don’t have a crimping tool, push the connectors in all the way, then use a flathead screwdriver to actuate the latch on the base of the connector. It should get stuck and firmly grip the sheath. Next, use your screwdriver to carefully push down on all of the metal pins at the front of the connector until they pierce the wires inside. Don’t be afraid to use a fair bit of force.
- You’re all done!
Extra Reasons Why Splitting An Ethernet Cable Is A Bad Idea
Splitting an ethernet cable is difficult, produces a low-quality cable, and will slow down network connections over the cable. There are a couple of additional concerns that make it an even worse idea, however.
First, many networking devices attempt to automatically detect the speed of your network and adjust their actions accordingly. Unmanaged switches, some routers, and other bits of hardware will try to figure out if the stuff you’re plugging in wants to talk at 10 Mbps, 100 Mbps, 1000 Mbps, or more. In theory, this is a great idea, as it means that the user doesn’t have to reconfigure their networking device each time they plug in a new device.
Unfortunately, the logic boxes on consumer-grade routers, switches, and extenders aren’t always amazing. In some cases, plugging in a 100 Mbps cord will cap your entire network at a max speed of 100 Mbps. This means that not only will your devices plugged in with fancy split cable get slow network speeds, but the rest of your devices will also be limited to a maximum speed of 100 Mbps. This isn’t ideal.
Second, some devices use ethernet cables to receive power. If you’re plugging in something that relies on power over ethernet, you’ll be forced to use a cable with the full 8 pins. This is because power over ethernet (PoE) uses some of the pins that you remove from a 4-pin cable to transmit power. If you’re plugging in a switch, extender, or access point without an external power supply, you absolutely cannot use a split ethernet cable.
Using Cable for Phone Lines
As it turns out, a 4-pin ethernet cable is very similar to a cable that might be used for a phone line. In fact, the only difference between a phone cable and an ethernet cable designed for a computer is the shape of the connector and the number of wires inside.
Older phone cables use RJ11 connectors, which have 6 pins, but only the central 2 are used. Newer phones and phone systems tend to use standard 8-pin ethernet, however, as it’s a lot easier to only work with one type of cable. In addition to the simplicity of sticking with one standard connector, the 8-pin cable can provide extra bandwidth for devices that need up to 4 lines.
In theory, you can split an ethernet cable in order to provide a split cable for phones. Make sure that you use the same set of wires in the same order for each connector. While this has fewer downsides than splitting an ethernet cable for a computer, it’s still not a great solution compared to buying an extra cable or a dedicated device to split the signal.
The Best Alternative To Splitting A Cable: Use A Switch
Networking professionals are very familiar with the problem of plugging lots of computers into a single ethernet port. In order to solve this problem, companies have made devices called “switches” for many years. These simple networking components can be quite inexpensive and neatly solve most of the problems involved with having lots of devices and very few ports.
While other devices like splitters and hubs exist, you’ll almost always want to get a switch instead of one of these alternative solutions. This is because switches have internal logic that cuts down on extraneous broadcasts and helps ensure that devices don’t talk over each other.
With a hub or a simple splitter, any signal sent to any device on the hub will be rebroadcast out to absolutely everything plugged into the hub. Since only one signal can be sent at once, this produces an incredible amount of network traffic and can grind a network to a halt. Switches, on the other hand, do their best to ensure that each signal is only sent to its intended destination. This means that multiple devices can talk and receive information at once with no issues.
You can also set up an older router to be used as a switch by changing the IP address, turning off DHCP, WiFi, and any firewalls. This whole process can be achieved in just a few minutes, allowing you to have a switch without spending any money at all.
However an older router might not be the best option here. It may not perform that well. It may also be limited to 100 Mbps if it is a little older.
Fortunately, switches that can easily handle a gigabit connection between two devices and a router are available for less than $20. Looks for brands such as Netgear, TP-Link, and Linksys. These switches are extremely simple to use. Simply plug all of your cables into any ports on the switch and plug in the power cord to the switch. You can get switches as small as 5 ports and as large as 48 ports, so there is surely a switch that can fit your needs.
Why Not WiFi
If you’re trying to connect multiple devices to a network and cables are an issue, WiFi may be a good solution for your problems. For most internet applications, WiFi is more than fast enough and can offer connection speeds well in excess of the 100 Mbps you’ll get on a split cable.
Additionally, there’s a good chance that one or both of your devices already has the ability to connect over WiFi. Most home routers have WiFi these days, and many ISPs will sell or rent you a modem with built-in WiFi functionality.
If your device doesn’t have built-in WiFi, you can often purchase a WiFi adapter that plugs in via USB or ethernet, and you can use devices like WiFi extenders, wireless access points, and mesh networks to ensure WiFi coverage of your whole house. WiFi isn’t perfect for every application, so if you’re playing latency-sensitive games or transferring massive amounts of information over the network you’ll probably prefer a cable.
Another underutilized solution that many people are aware of are powerline and MoCA ethernet adaptors. These allow for wired network connectivity using existing electrical wiring (powerline networking) or coaxial wiring (MoCA networking).
It is technically possible to split an ethernet cable, however it is not a great practice. It is likely to not deliver the results you want. It is also likely to be unreliable due to signal integrity issues.
Ethernet switches make it easy to connect multiple devices to a single ethernet port. Switches come in all sizes ranging from 5 ports all the way up to 48 ports. The smallest of switches can be purchased for $20 or even less.
When choosing a switch always make sure it is a gigabit switch. There is no reason in 2022 and beyond to purchase 100 Mbps switches. They are simply out of date technology and cost virtually the same price.
Avoid splitting ethernet cables, it is more trouble that it is worth.