Larry the cable + ethernet guy

April 1, 2012 2:49 PM

Larry the cable-and-ethernet guy? How did he figure out my home's ethernet topology?

So when we moved in, the cable/DSL guy was able to figure out which ethernet cable went where. I told him 'upstairs office' and he plugged the right cable in (I was away doing something else when he performed his magic.)

In this photo I know that the ethernet comes into the wiring closet via a blue and orange cat 5 drop. The mass of purple cables indicate different cat5 jacks throughout the house. So plug the incoming cat5 cable into the router and the proper purple cables into the router and internet is dispersed throughout my crib.

But, how did he know? there are no labels on the cables. Did he run around to each jack and verify the connectivity?

posted by toastchee to Computers & Internet (6 answers total)

I'm not sure what you're asking?

The "router" has two sides, internal and external. The special orange one is obviously the external and all the rest all go into the internal side. There is nothing special about any of the internal wires, except they all should be attached to the same network.
posted by Threeway Handshake at 2:58 PM on April 1, 2012

Best answer: He probably used a tester like this. First plugged the end into the socket in your upstairs office socket and then plugged it into the other ends in your wiring socket until he saw the signal.
posted by Disco Moo at 2:58 PM on April 1, 2012 [2 favorites]

Disco Moo has it -- he didn't chase down the end of every cable, he plugged one end of a continuity tester into your office jack and then checked every cable end at the router until he got the right one.
posted by briank at 3:11 PM on April 1, 2012

Best answer: I would actually expect him to have a more general-purpose toner that works with coax/phone as well as cat5. It generates a tone on one end of the wire, and you use the little wand to listen for that tone at the other end. If he was feeling charitable towards the techs of the future, he'd then label whatever he toned out.
posted by kavasa at 3:17 PM on April 1, 2012

Best answer: If he was even cooler he used a tone detector. You plug a little tone generator box into the jack in the office, then in the closet you have this wand thing with a needle like tip and a speaker, you wave the wand around the ends of the cables until you find the tone. This is much faster than a full blown cable tester where you have to plug into each cable in turn until finding the right one. It's also way more useful when you have old punch blocks with hundreds of lines. Just wave the wand until you find the loudest one.
posted by zengargoyle at 3:21 PM on April 1, 2012

If he was even cooler than all of the above he just made sure a computer or other device was plugged in to the upstairs office jack, then plugged in cables one at a time until the router lit up indicating a signal on the port. Takes maybe 5 minutes.
posted by mmoncur at 8:46 PM on April 1, 2012 [1 favorite]