[lug] testing for straight versus cross-over patch cables?

[Nate Duehr]

On Sun, 2002-08-11 at 21:00, j davis wrote:

> also....i know everyone know this but...
> generally if the cable is yellow its a crossover cable and
> sometimes the outside shielding  will say "crossover" really small too.
> all ot the above only applies to pre-manufactured cables.

Don't take this the wrong way but...

Bzzzt.  Wrong.

You can order cables of whatever pin-out you like in whatever color you
like from multiple vendors.  

Yellow is definitely NOT any kind of standard on what pin-out the
connectors are configured as.  (I have at least four yellow
straight-through, commercially-manufactured cables in my basement right
now... one of which is definitely beyond the normal working length for
Ethernet too... gotta love cable manufacturers... they'll build
anything, even if it will break your network...)

Also, I have never seen a bulk cable manufacturer print anything about
the pin-out of the cable on the jacket.  (Remember, there is no shield
on UNSHIELDED TWISTED PAIR [UTP] cable.)  

Any vendor that does is probably charging you too much for the cable
anyway, as the machines to label thousands of feet of UTP cable jackets
with "cross-over" are going to add unnecessary cost to the product.

However, the sad state of the computer industry is probably such that
maybe they really are doing this now... people don't bother to learn the
relationship between two silly pairs of wire anymore... pins 1,2,3 and 6
are all that you need to know to make any Ethernet cable your friend...

Ahhhh... no one remembers the joy of DTE/DCE serial cables, eh?  In
fact, if you look at the electrical properties of a data circuit and
realize that's all Ethernet is... it becomes amazingly clear why you
have 2 pair, and why they have to cross when connecting to two "DTE"
devices... whereas a switch or hub is a DCE device, to use the old
terminology...

Ever had a cable that had the internal color code screwed up (never did
find exactly where... but the colors crossed inside the cable, which
meant it had been SPLICED inside, and that's bad...) and LOOKED correct
but wasn't when you took a VOM to it?  I have.  Once.  Wasted a lot of
time figuring THAT one out... of course, Cat 5 was hideously expensive
back then also, and we weren't wasting any of it... 

Personally, I buy PINK cross-over Ethernet cables to carry around with
me and take to customer sites, after a friend of mine started it as a
joke.  The joke started at a company I worked for that seemed to think
everything needed to be certain colors instead of having technicians
that were smarter than the cables they were using... so since he was
writing the specification with that in mind... the purchasing folks
happily bought pink stuff for some specific connections to a specific
network device that had to be wired directly to another terminal
device....

They're immediately noticeable, and no self-respecting
testosterone-laden network jock fresh out of Cisco "engineering" courses
who can't build his own cables will steal them from my laptop bag while
I'm not looking.  :-)  

(No offense if there are any testosterone-laden Cisco-jocks present... I
just get a serious belly laugh out of someone who can program some
monster 150+ port Ethernet device who can't make an Ethernet cable from
memory... it's so wonderfully ironic... if you really want to get me
started, let's talk about not using RJ45's built for stranded conductor
wires on solid conductor Cat 5... yes, there *IS* a difference in
RJ45's... and it won't bite you until you build about 300 of them in a
weekend... or should I say, not until Monday morning, anyway...)

Sorry, I'm ranting, and it's not directed at you, JD.  I'm pushing over
windmills here, methinks...

-- 
Nate Duehr, nate at natetech.com