Last updates: 21-Jun-2009

Warning: This hack will not just void your warranty. It will drop-kick it to the floor, stomp it in the gonads five or six times, shoot it in the head, douse the body in petrol and set it ablaze THEN spit on the remains for good measure. And that doesn’t take into consideration what it could do to you or your equipment . You have been warned. Don’t try this unless you’re comfortable with multimeters and soldering irons.
Now, on to the good stuff. Suppose you have a Linksys WRT54G router & antenna that you want to mount somewhere, say on your roof. So, one fine Saturday morining, you grab a few tools and get to work. About 35 minutes into your little project, it hits you: How exactly do you get power for your router? The roof has no power outlets and you need to keep the antenna cable as short as possible to minimize signal losses.

You start wondering, “Maybe I should have gotten a Meraki. They come with Power Over Ethernet(POE).” Then, it hits you, “Wait! Maybe I could run some power over the ethernet cable…” So you do a little scholarly research(a la google) and find a few people who have modified their routers to support POE.
Basically, ye olde ethernete cable has 4 pairs of wires, each pair consisting of a solidily coloured cable and a white-striped cable of the same colour. The usual arrangement(TIA/EIA-568-B) for most patch cables is:

100BASE-TX makes use of wires 1,2,3 & 6 to transmit and receive data, leaving wires 4,5,7 & 8 for our use.

Update: I forgot to mention. Once you do this hack, you have to remember that if you power the router up in the normal manner, power will still be supplied from the power terminals to pin 5 and pin 8 on the WAN port. Keep this in mind if you’re connecting the router to other equipment to avoid …unexpected results. I use a customized cable that has wires 4, 5 ,7 & 8 cut and terminated in the middle of the cable just to be safe

First we need to do is solder a couple of wires, one from pin 5 to the positive terminal on the router’s board and the other from pin 8 to the negative terminal. This will transfer the power coming in over the cable to the power jack on the board where the router can make use of it.
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This is the only modification that needs to be done on the router itself. However, don’t pack everything up until you’ve tested to make sure its working.
Next up will be our injector. Now, there are many ways to feed power into the cable. You can buy a power over ethernet injector, splice the power cable directly in the network cable or build your own injector. I’d recommend buying a power over ethernet injector; it’s a more reliable option and you don’t have to mutilate the poor cables.

But then, if you’re reading this guide, you probably don’t have an injector available or are thinking,”Building my own POE injector is just so much cooler!!” In that case, you’ll need a keystone jack, a spare ethernet cable, and a power brick for the router (It’s usually better to get a spare of equivalent rating as the original since these instructions will make it …unwieldy for normal use)

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What you do trim off one end of your ethernet cable and connect wires 1,2,3 and 6 to the jack. These are your data lines.

Then you take the plug off your power brick and connect the +ve to pin 5 on the jack and the -ve to pin 8. Trim off any unnessary lengths and you have your own power injector.

Once that’s done, feel free to call all your friends and gloat over how clever you are.

Router:

Power Injector: