Ethernet Tag Team – SmallProtos

Or: How to double throughput on an ethernet cable. This trick could come in handy if you find yourself in a position of needing to run another 100 Mb/Sec ethernet cable alongside an existing one.

As an example, I found myself needing another 100 Mbit cable in my house when reconfiguring my home network when I got UVerse. UVerse transmits TV over TCP/IP, so it can (in theory) be sent through routers, switches, etc. Unfortunately I found that the TV service would die occasionally if I did not have a dedicated ethernet cable running directly from the UVerse “Residential Gateway” to the set top box. For some reason it just didn’t like my home network, and would just randomly fail. So I was forced to run another long cable dedicated to my set top box to make it work flawlessly. Bummer.

Then it occurred to me that I didn’t really need to run a separate physical cable, I just needed to get 2 cables out of the one that was already run. How could I do that? Well as it turns out, CAT5/5e cables only use 2 of the 4 pairs of wires inside them, leaving the other 2 pairs available for… you guessed it…. the other cable I needed. All that was necessary was to cut off the ends of the cables and install new ends so that there would effectively be 2 cables inside one jacket. That was a lot better solution than having to run 100 feet of new cable.

Here’s a drawing of an ethernet cable using EIA-TIA-568A wiring:


The table below shows a connection pinout that can be applied to both ends of the cable in order to get (2) 100 Mbit cables in one.


As you can see, connector 1 uses regular 568A wiring, and connector 2 uses the same thing, except that we substituted colors. Two pairs are used for each 100 Mbit connection.

Both ends of the cable will now have 2 connectors, yielding 2 100 Mbit Cat5 cables from 1 physical cable.

Unforunately you can’t use this trick with gigabit ethernet since all 4 pairs are used for the gigabit connection. If you’ve got 100 Mbit though, you can use this technique to “run another line” without pulling any more cable. If you have a complicated cable run going through walls, which may be the case with pre installed home wiring, this may be useful since running a cable through the same path can be quite difficult.

More information on Cat5 cabling can be found here as well as many other resources on the web.

If you find this handy I’d love to hear how you applied it to your situation :)

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