Do you have enough Cat5?

Like me, you might have sneaked a few CAT-5 cables into the walls when you were decorating, or maybe you've strung some across the loft to move your network from place to place.

You probably also thought, "Hey, I'll never need more than a couple will I?" - So did I , until I needed a 3rd to the same place for another device.

So, there is an easy answer here, put in a Switch, or a Hub. However, this is another Switch in your network, and it uses a few watts of power also.

How about a nifty way of running two CAT5 100mbit connections across ONE CAT-5 cable?

What's the catch? - Well you can't use this hack if you're running Gigabit networking, as it's only good for 10mbit, or 100mbit.

How does it work? - No secrets here, 10mbit, or 100mbit ethernet only uses TWO pairs out of the four on the cable. Therefore if you create a couple of adapters you can feed two connections on one cable.

This technique is mentioned here in Wikipedia

Wiring

I wired up the RJ45 plug as a standard T568A cable - see here for the colours, and then used 2 keystone RJ45 sockets, wired like this (The pic is from above, with the socket 'holes' at the bottom.

If you have a RJ45 cable tester, use that to make sure you have 2 good pairs on each end (you'll need to plug the two 'plugs' together using an 'end-to-end' adapter, of if you're like me, you just went for it and connected it up. The resulting diagram explains what is going on here:
You can also (in theory), according to the Wikipedia article, use this for running 1 x 100mbit Lan, and up to two Phone Lines provided your phone lines only require 2 wires, or 4 if you run just one - Running Phone lines over this type of setup may be forbidden by your telephone company, so beware before starting on this for that reason - you will also be likely to get interference from the LAN signals on your phone calls due to the unshielded nature of the cabling.

DISCLAIMER: Please dont attempt this if you're not confident in making up CAT5 cables, I assume no responsibility or liability for any injury, loss or damage incurred as a result of any use or reliance on this information. 8-)