[Tfug] Yet another poser

[Rich]

On Sep 14, 2007, at 12:23 pm, Bexley Hall wrote:

> So, in as much as is possible, I have tried to
> rid myself of this problem by "picking" what I
> think is an appropriate "standard" cable and
> then building "widgets" to append to said
> cable to modify it's *overall* character.
I found a site a while ago where a sysadmin listed  the contents of  
his (custom-built) cable kit. It was something like this:

  - standard T568B to T568B cable
  - 1" crossover adapter m-f
  - 1" loopback adapter m-f
  - RJ45-db9 (Cisco)
  - RJ45-db9 (RS232)  2 off
  - db9-db25  2 off
  - db9 and db25 gender benders, each 2 off
and the clever bit:
  - an *RJ45* null modem adapter - 1" long again

I forget what the rest was. I'd've thrown in a USB-db9 adapter for  
fun and learning.

Well, I *say* I found a site -- well, I *lost* it again.

> Of course, the more *interesting* widgets are
> those that actually alter the effective wiring
> of the cable -- not just the gender of the
> connectors on its ends.  For example, one widget
> is a "null modem" which, of course, converts
> the generic cable into a "null modem cable".
> Another widget swaps the "port A" and "port B"
> connections on some older SPARC machines.  Still
> another converts the generic cable into one
> suitable for use as a "PLIP" cable.  :>
...and all these could be integrated into the above.

> It's a cakewalk to turn one of these "RJ45 widgets"
> into a "crossover" widget.  I.e. swap pins 1&3
> and 2&6, then glue the thing back together.
Bingo!

> The question becomes what to do with the other
> 4 conductors in the "widget".  I suppose to
> truly mimic a crossover cable, they should be
> present and run "straight through" -- is this,
> in fact, how "real" crossover cables are wired?
> Or, do vendors skimp and simply *omit* these
> extra conductors to save a few millipennies?
They're all there in every x-over I've seen.

> Lastly, how are crossover cables typically
> identified?  I had assumed I would just slap a
> label on this (I label all of my widgets since
> you "can't tell the players without a program"!)
> saying "CROSSOVER"...?
Yellow band at one or both ends.

Not a problem for me, because I label every cable at both ends with a  
labelling machine. If it's not a crossover, it's labelled:

1. hostname
2. (IP, unless dhcp)
3. MAC address
4. wall socket

> (Yeah, I think WAY too much about these little
> details... :>  )
Taha! You're not the only one!

R.