(Almost) Making An Ethernet Port Splitter

Have you ever seen those devices that say they will take one Ethernet port and split it into two? If you have, then you have no doubt thought that the promise of such a contraption could be invaluable where adding another Ethernet port would not be easy or possible to do.

I've seen these devices before and knew that they existed for both Ethernet and Token Ring. I was always curious to try one, but the cost kept me from doing it. It wasn't worth the price just to find out that it might not even work.

The curiousity--however--stayed in my mind and a while ago I happened across some Ortronics OR-60950049 category 5 plug assemblies and wall mount plates. After getting these and thinking about it for a while, I decided that I would see if I could "misuse" these to make an Ethernet port splitter. This page documents the experience and the failure of it to work when I was done.

I started the project simply enough by using the Ortronics connector as intended, just to be sure I had the pinout right. I cut the end off of a piece of CAT5 patch cable and inserted each wire into the "press" connectors at the back of the wallplate.





After getting the pinout right, I had the idea to see if I could make a splitter by wiring two of the Ortronics connectors in parallel with one another. In and of itself this didn't take too long to do. There was something else I had to do first.









I needed to build up a computer so I'd have enough machines to test this theory! This took a little extra time to do.

Now I had a computer for one port. Due to time constraints, I borrowed my dad's laptop for the second computer that would be connecting via my splitter.

At first I used a Linksys USB-200M Ethernet adapter on my dad's computer because I was not sure how this would end up working out and I didn't want to smoke his onboard Ethernet hardware should something go wrong. I attached cables to the two plugs in the Ortronics wall plate and powered both computers up.

When both computers had finally booted, I learned that the network cards were basically fighting one another for "dominant" status. At fist the Realtek 8129 in the HP desktop computer would link up, then the Linksys adapter would try to establish a link, thusly knocking the Realtek adapter off the network.

Using the onboard Realtek 8139 in the laptop with the 8129-based card in the desktop computer, things went a bit better. The two NICs weren't fighting with one another and after a moment they did settle down. When both of them appeared to have a link, I tested both computers. To my dismay only the desktop had any connectivity. The laptop stubbornly refused to access the network for any reason.

Now that the end result is obvious, I'd like to know why this didn't work. I would assume that there is some kind of circuitry used in the commercially available splitters that makes both NICs play nicely on the line. If you've got any thoughts, write me.