How-to Make Your Own Ethernet "splitter"

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Introduction: How-to Make Your Own Ethernet "splitter"

About: http://www.christophecaron.com

With an Ethernet "splitter", you can simultaneously connect two computers (or other network devices) on one Ethernet cable. You can buy Ethernet splitters for approximately $ 20.00 USD but you also can make your own.

Context:
One office, one ethernet jack and two computers, or
One living room, one ethernet jack and one HTPC and one XBox.

If you can't realistically (without tearing apart walls or renting a scissor lift) pull one more ethernet cable from the patch panel to the office / living room etc. you can consider the use of an Ethernet "splitter".

I'm assuming all the four pairs of the ethernet cables are properly connected within the ethernet wallplate and the patch panel.

Step 1: What You Need

In order do make your own Ethernet splitters you'll need the following:

  • Two RJ45 Crimpable Plug
  • Four RJ-45 keystone jack
  • Short Ethernet Cable Scrap (approximately 2 feet)
The tools you'll need:

  • RJ45 Crimp Tool
  • Craft knife
  • 110 Punch Down Tool
  • Loctite Super Glue

Step 2: Crimp the RJ45 Plug to the Ethernet Cable

...using the following wiring scheme:

1 White/Orange
2 Orange
3 White/Green
4 Blue
5 White/Blue
6 Green
7 White/Brown
8 Brown

Taken from the excellent Hardware Book: www.hardwarebook.net/cable/network/ethernet10basetstraightthru.html

Step 3: Punch Down the Other End to the RJ-45 Keystone Jacks

Take the other end of the cable, cut it to 9 inches and punch down the four pairs using the following wiring scheme:

  • Jack #1:

1 White/Orange to pin 1keystone jack
2 Orange to pin 2 keystone jack
3 White/Green to pin 3 keystone jack
6 Green to pin 6 keystone jack

  • Jack #2:

4 Blue to pin 2 keystone jack
5 White/Blue to pin 1 keystone jack
7 White/Brown to pin 3 keystone jack
8 Brown to pin 6 keystone jack

Once all the pairs are punched down, you can glue together side by side the two keystone jacks.

Step 4: Make One More Splitter

...using the previous information so you end up having two splitters.

Step 5: Plug One Splitter to the RJ45 Wallplate

... and plug the two computers to the splitter.

Step 6: Plug the Other Splitter to the Patch Panel

...and plug two patch cords from the splitter to two free ethernet jacks from the switch. If your splitter connections are right the two leds "LINK" from the switch on which the patch cord are connected should turn on.

Step 7: Final Words

We now have two computers simultaneously connected using only one ethernet cable. This method is similar to PoE (Power over Ethernet) but instead of injecting DC, it is injecting another "data".

But again, it is better if you can to pull one more ethernet cable from the patch panel to the wallplate. But in some specific cases, the Ethernet "splitter" can help out.

2 People Made This Project!

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146 Discussions

I want to be able to split an Ethernet cable that has PoE to power 2 PoE devices and both fall well under the 15W max combined. Is this possible? So I can use the 2 wires carrying the 48VDC to power both devices, but that leaves me 6 wires to split the data. Can I do it hub style, like put the same 4 data wires to both devices?

1 reply

If they are VOIP phones this spliter should work. It is actually the only way ive ever seen it work. I have never seen these work for PCs. Been doing IT work now for 15 years.

I wouldn't be surprised. I've never actually tried such a thing but I can't imagine why it wouldn't work. You might get a slower connection because you're basically splitting your internet in half though, presuming both your laptop and your router are on, though I don't really know how overall usage works when multiple sources are using it right from the same line.

This "splitter" works well as long as it is very short and it works only with 10Mbps Ethernet and not 100Mbps (for which you need all the pairs).

It will not work for long cables because you are affecting the line matching.

This splitter basically is a good artisanal solution but from an engineering point of view, meh... it's a miracle that it works :-/

That is not correct FrancoM9. The 10/100Mbps Ethernet only uses 2 pairs of the 4 pairs in the cable. It is only Gigabit Ethernet (1Gbps) that needs all 4 pairs. The line matching is not a problem because you are using 2 previously UNUSED pairs. I have successfully used this technique (the splitter/combiner is called an economiser in the UK) over a 30m long Ethernet cable. Of course a switch is easier to use, but if you have the RJ45 connectors and some patch cables on hand the economiser trick is worth trying.

Cat5e which is only rated for 10/100 MB/s up to 100 meters requires all 8 pairs. These spliters only work for VOIP phones and not complete data.

i have tired it. it doesnt work well. actually in my experiment i made two ethernet wire from one. then the one i plug into the laptop and other one to the router.while laptop turned on both (laptop and router) doesnt get any internet access, barely laptop works well with internet access but not the router.

while laptop turned off router works well.

Data for Computer Networking requires all 8 pins and cannot be split this way. In my 15 years of working with Computers and Computer Networking I've never seen this work for PCs. However if you are using these to hook up 2 VoIP (Voice Over Internet Protocol) phones it will allow both phones to work because phone data only requires 4 pins.

The basic principle in this article makes sense and should work. However - CAUTION - when punching down the conductors in the two jacks use the designations found on the jacks AND NOT THE PICTURE! The pin-outs on the jacks vary from manufacturer to manufacturer. That may explain why some folk can not make it work.

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JonE13

2 years ago

In an Ethernet cable there is 8 wires, but only 4 are being used. let's say the 4 wires being used are the two brown and the two orange. let's also say these 4 wires occupy the slots 1, 2, 3 and 4 on the Ethernet jack. the 4 remaining wires are two green and two blue, which occupy the slots 5, 6, 7 and 8 on the Ethernet jack. What would happen if you have the two brown and the two orange wires and the two green and the two blue wires split at each end. (on each end you would have two groups of wires.) the brown wires are connected to the slots 1, 2, 3 and 4 on the Ethernet jack on each end. and the two green and the two blue wires connected to the slots 1, 2, 3 and 4 on another Ethernet jack at each end. (now you would have two Ethernet jacks on each end of the cable with wires connected to the slots 1, 2, 3 and 4.) Will this work or not? I can't see any reason to why not, but you never know. As the author of this instructable said, this is very similar to power over Ethernet, but only with two data lines instead of one data line and one power line. The fancy picture below should help explain anything confusing (everything). (Sorry for any bad English)

dobbel Ethernet ide.png
2 replies

Yes. It works. I have done exactly that 10+ years ago because I couldn't run a 2nd cat5 cable through the tubes (filled with telephone cables already). Make sure you follow the right paring: pairs should end on 1&2 and 3&6 on the wall socket. You will be limited to FastEthernet (100 MBit) though.

It's a little late now. I found my dad's old ethernet splitter from the 80's and it works fine. But thank you for answering my question anyway, it might be useful someday :)

Hi there,

I'm going to do this setup: 2 splitter at the start and at the end of ONE wire, in order to connect 2 devices with a single wire. It is possible? At one side there are connected 2 devices, on the other side is connected to the splitter and then to TWO different ports of my switch.

Thanks.

can u just hook it up directly to another wire.......i can't afford the connetctors

splitter 2nd port not working plz help me. 1st & 2nd port use to internet purpus .not use to data & voice .

You said 'This method is similar to PoE (Power over Ethernet) but instead of injecting DC, it is injecting another "data". ' which is kinda misleading.

Power over Ethernet is a negotiated protocol between the device and the switch, while still allowing the use of gigabit speeds using all 4 pairs.

You're thinking "Power over Cat5/6" which is where the spare pairs have 5 or 12 or 48 Volts and no negotiation. Don't ever plug anything gigabit into this.

These splitters do work, but are more likely to induce crosstalk between the two pairs of twisted pair inside the one run of cable. Yes I have used them as a last resort, but a local switch, or man-up and run some more cable is a far better way to go.

Cabling is almost always better than wireless ethernet.

I'm just going to add this as a note: if you are trying to achieve faster speeds with Gigabit Ethernet, this is not going to work, as Gigabit uses all the pairs on its own, if you take away half of them it WILL limit you to 100mbps.