[COLUG] Figuring out which ethernet cable is which

[jep200404]

Mike Harrold wrote:

> What is the simplest/cheapest way ... to figure out which cable it is (and
> for that matter, all the others so I can relabel them).

Angelo McComis wrote:

> Easiest: put a device (laptop) at the far end and connect it 
> to the nic. In the basement, try each of your leftover cables 
> in a switch til you find a link light.

That's pretty darn good, as it can be done by one person alone, 
and doesn't require any extra equipment. 

I can improve that a bit. 

Upstairs, unplug all ethernet cables. 
In the basement, plug _all_ cables into the switch. 

All the link lights should be out. 
If not, figure out what you forgot to unplug upstairs 
or label the cables as stuck on mysteries. 

Then for each cable end upstairs: 

   1. Plug it into a running computer*. 
   2. Go downstairs and see which new link light turned on. 
   3. Label that cable. 

* A laptop with a good battery would probably be easiest. 
  A hub or switch that can connect to another switch 
  would work also, and doesn't require booting, 
  but does require external power. 

Jim