Hi there, I have been trying for several hours now to make an ethernet splitter.
I have a laptop, and I dont really want to be carrying around a large hub along with its power pack, so I decided to get two ethernet interfaces (RJ45 female), and connect them to a male RJ45. I have connected it to my network, and it works perfectly when I plug one PC into it, but as soon as the other one goes into the other interface, it screws up.
I have thought about it, and I have come to the conclusion that the reason it is having trouble is because it is trying to connect my PC to (A) a hub and (B) another PC, which requires two totally different cables to connect to each device (crossover/straight through).
I am now totally confused because I had always assumed that this is how a hub works. I would appreciate any information that anyone could give me on how to solve this little problem of mine... thanks in advance :¬)

James

As far as I know... you cannot split an ethernet connection. A device (such as a computer) first establishes that it has a connection on the line (hence the link light) and then tests if it is clear to transmit. It emits a packet and if it is clear, it transmits. If it is not, there is a collision and both devices that were vying for the transmit opportunity both quickly generate random time intervals to wait before trying to transmit again. This is what is known as CSMA/CD (you can look it up for a better explanation, if you wish). In small networks, all this traffic isn't a problem because all of this is actually negotiated and done in nanoseconds and then physically at the speed of electricity (which isn't quite the speed of light, but still pretty darn fast). A hub will take these signals and repeat it to each device linked up to it's interfaces. A switch (necessary in larger networks) will avoid repeating all of that traffic and it will actually learn where all the devices are and "route" frames directly to the interface they need to go to. I have never, ever seen an ethernet splitter and a hub does much more than just physically splice ethernet connections. I don't see any way to get around using a hub. I would suggest buying a small DLink or NetGear 5-port hub (about $30-$40 last time I checked). I have one and it's pretty small (3" X 4.5" X 1").

a hub is a repeater. a cable is not.

They're getting hard to find, but I'd suggest looking for a pocket passive hub. Passive hubs do not need power, so you won't need to worry about the power pack and they are very small [hence the name pocket hub]. If you check with stores that sell used equip, you should be able to find one for about $5. If you can't find one, then you'll need a "normal" active hub which is a repeater. I've seen a 5 port hub/repeater as low as $15.

You can by CAT5E splitters for connecting 2 devices through 1 cable. You should be able to make one.

The secret is to use the two unused pairs. A CAT5E cable that operates at 100Mb is only using two of the four pairs for data. In most cases the remaining two are unused.

So in theory if you connect two pairs from the male RJ45 to one of the females, then the remaining two pairs to the other female.

HOWEVER...by doing this, and using all four pairs, you lose the error correction ability.

The only time whereby all four pairs are used is when there is a device that draws its power over CAT5E, or Gigabit over CAT5E.

Hope this helps a bit, and even makes sense. LOL