OT: cat 5 cable, ethernet, connection jacks

[Madison Kelly]

Matt Price wrote:
> hey folks,
> 
> Hope it's ok if I ask a networking question here... I'm planning to
> lay a bunch of ethernet cable in a room.  I have these fancy Leviton
> RJ45 female jacks and am running the cable through wolding, so having
> many cables come out of a hub is a royal pain.  The computers in the
> room are arrayed along a straight line.  Is it at all possible to use
> the RJ45 jack as a simple junction connecting two pieces of cat 5
> cable?  This would look something like this:
> 
> 
> ----		   ___________			__________
> |hub|--------------|rj45 plug|-----------------|rj45 plug|
> -----		  ------------			---------     
> 		      |				  |
> 		      |				  |
> 		      |				  |
> 		 Computer		       Computer	       
> 
> I imagine this is impossible, or people would do it all the time
> instead of using hubs...  anyway, if someone can explain to me at
> least why it doesn't work, that'd be a help.
> 
> thanks,
> 
> matt

   Well, strictly, no you can't. Realistically though, if you are in a 
pinch, you can run two runs through one RJ45 cable but you will probably 
have trouble with cross talk... Hard to say, I've never done it. If you 
want to try though, here's the idea:

   Normally only pins 1, 2, 3 and 6 are used (one pair on 1/2, the other 
pair on 3/6). You can try splicing the cable back a few centimeters and 
run the four other wires to pins 1, 2, 3 and 6 of a seconds cap. So say 
you normally use the green pair on 1/2 and the orange pair on 3/6, run 
the blue pair to 1/2 on the second cap and the brown pair to 3/6 on that 
second cap.

   Now run the cable to the far computer but give yourself a little 
slack where you want to tap into the closer computer. carefully splice 
the green and orange pair just enough to reach the teeth of the female 
jack. Leave the pairs twisted until just before the teeth... your 
connection is going to be degraded enough without helping it :p. Don't 
splice the blue and brown wires though, let them pass through to the far 
end and punch them in where you normally would have punched in the 
green/orange pair.

   Again, use this at your own risk... I know theoretically it will work 
but I wouldn't recommend it unless the second run really would cause 
that much trouble. If you do try it though, it will look something like 
this:

                   [ Computer 1 ]      [ Computer 2 ]
                         |                   |
[ Hub ] =>--------------+-------------------/
         ^- [ Two caps ]

HTH

Madison
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Madison Kelly (Digimer)
TLE-BU, The Linux Experience; Back Up
http://tle-bu.thelinuxexperience.com
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