PoE question

Does anyone know if there exist ethernet switches that are powered via power over ethernet? I know there are a lot of switches that *provide* PoE, but I’m wanting one that I can put in my crawlspace and feed power to via an ethernet cord.

It’s going to be a pain if I have to run power down there, hence the question. Thank-you ahead of time for any information.

  1. I know there are a lot of wireless access points that use PoE, It may be a good place to look as they may have some Ethernet ports on them you could use. Out of curiosity, why not use wireless?

  2. I like to keep the wireless network on the untrusted side of the firewall (orange zone), and only allow wired connections on the trusted side (green zone). Then I only allow access to windows shares and other resources from the internal network.

    It’s not perfect, but it’s a good first step to protecting the windows machines on my home network. Also, wired connections are so much higher bandwidth and higher reliability, so I prefer them when they make sense.

    Oh, and good call on the PoE waps. That sounds like a good place to look.

  3. Well the problem lies in the fact that you can’t put too much power down a standard twisted pair wire. Especially for any considerable length, 13 watts I think? (Linear Technology has all in one chips to do the switching for you if you wanted to homemake one)

    What I think you could probably do to simplify things is to create your own cable. Simply bundle (wiretie, heat shrink, electrical tape (ew)) something like a 2 or 4 wire cable ( 20 or 18 gauge) to an ethernet cable and run it all the way down there and plug into the box. On the side where you would be plugging it into your upstream switch/router just use a wall wart there and wire into that low voltage cable.

    2 and 4 wire cables can be purchased fairly easily from most hardware stores, its often used for doorbells and irrigation control valves.

    Now for the practical side of things…. crawlspace? I’m not sure how long a piece of electronics would last down there without experiancing dendrite growth on the PCB (you’d probably want to conformal coat it or something, then figure out a way to seal the rj45s)

  4. I’ve considered the effects of the crawlspace on the switch, and I just can’t decide. I actually grabbed a cheap Baystack 301 off ebay for experimenting with. The spec-sheet says that it’s capable of operating in 85% non-condensing humidity.

    I still haven’t decided.

    See, it’s one of those things where it will save me tons of cable if I put the switch down in the crawl. If I run all the wiring into the server closet, that’s gonna be about 3x more wiring than the switch in the crawlspace method.

    Ah well. Lots to think about.

  5. Just an opinion, but I don’t see much use in putting equipment in hard-to-reach places. You’ll be kicking yourself when the network HAS to get back up NOW and your switch is buried down in spiderland. You’ll have to watch out for traps and pits, and put something equally heavy where the switch is located…only step on the white tiles!

  6. The idea here is that it’s just a switch. It’s about the most innocuous piece of network hardware in existance. Does anyone really reset their switches that often?

    Although the thought of having to go all ninja-mode to reset the booger is annoying, I’d probably just go in the garage and flip the breaker that it was on. A bit overkill, but very doable.

    Or, if the booger were connected via PoE, then I just disconnect and reconnect the ethernet cable that is providing it power. Even easier!

  7. I think the point is not what if you have to reset it…. I’m thinking more along the lines of… what happens when it goes kaput and catches fire…

  8. Well, a damp crawl space is less likely to catch fire than a desk full of dry paper.

  9. Well things with electric power sources can self sustain a flame….

    “Dave you can turn it off now. Ok, Dave you can pull the plug. DAVE Pull it out!”

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