[lug] cat5 cable problem

[Nate Duehr]

Jeff wrote:

> Hi folks,
> I'm trying to make a cat5 cable using cat5e, not simple cat5.  After I
> put the ends on (regular RJ-45) the lights on my switch just sit there
> and blink at me.  I've checked the cable order several times and it
> looks ok.  Any ideas on what I'm doing wrong?  Thanks.
> Jeff

Haha, in a word... "No."

As Dan mentioned, check it with a meter.  Assuming you're trying to make 
a straight through cable, pins 1, 2, 3 and 6 as viewed left-to-right 
from behind the connector (cable side with the tab down toward the 
floor) need to have continuity end-to-end with no swapping.

I've taught a whole bunch of people how to do cabling, so here's the 
basics... there's always more to learn, but this'll cover a lot of it.

Looking down from connector from above, with the locking tab on the 
OTHER side... these are the pins used for 100 Base T Ethernet.

_______________
| | | | | | | |
1 2 3 4 5 6 7 8

|-| |-----|

Cheap meters are available that are nothing more than a 9V battery and 
continuity testers for the pins.  They work okay for home networking, or 
a standard multimeter in continuity test mode will do in a pinch when 
you have a problem.  I've made enough of these that if I make one and it 
does not work correctly, I usually just snip the RJ45 off and start over.

For more money, testers can be had that will check cable cross-talk, and 
other tests to determine if the cable really meets Cat 5 or higher 
specifications.  They can run into the thousands of dollars.

A good quality crimp tool is a must if you do a lot of these.  I 
recommend Amphenol.  The plastic ones that crimp from the side are 
typically junk and will a) crimp things unevenly leaving open circuits 
on pins 1 & 2 quite a bit, b) wear out after a couple of hundred 
connectors making them even worse over time.

The Amphenol RJ45 dies and crimp tools are not cheap, however... but 
they crimp "end on" or straight on toward the pins and because they're 
made out of die-cast tend to last much longer.  The removable die means 
that when it does finally wear out you can replace it easier, and you 
can also do RJ11/12 and other connectors in the same tool by just 
grabbing a small screwdriver and changing out the die.  These tools run 
about $70 last time I looked, so unless you're making at least 20 cables 
(40 crimp connectors) -- just buy ready-made cables and be done with it.

The color-code specifications can be different between manufacturers, 
some use EIA/TIA 568A, some use EIA/TIA 568B -- but the one I've always 
used for straight-through cables (and can't remember right now which one 
it is) is:

Primary Color  Secondary Color  Pin #
-------------  ---------------  -----
White            Orange           1
Orange           White            2
White            Green            3
Blue             White            4
White            Blue             5
Green            White            6
White            Brown            7
Brown            White            8

The memory techinque to remember this one is:  "Split Green, Flip Blue."

The cross-over cable for going DTE to DTE between equipment would be one 
end with the above wiring, the other end would be as follows:

Primary Color  Secondary Color  Pin #
-------------  ---------------  -----
White            Green            1
Green            White            2
White            Orange           3
Blue             White            4
White            Blue             5
Orange           White            6
White            Brown            7
Brown            White            8

This is for standard Ethernet cables... Gig over copper, stuff like 
that... I have not done anything with.  I assume the Blue and Brown 
pairs are used, and these will probably not work.  But I've never looked 
into it as I've never had an application where I wasn't using fiber for 
anything faster than 100 Mb/s.  Just a disclaimer, I really don't care 
to know the answer at this point.  :-)

Be careful -- Amphenol and others make different kinds of RJ45 
connectors depending on whether your wire is solid-core or 
stranded-core.  They're very difficult to tell apart unless your 
eyesight is very keen and you've worked with both types.  Even then, 
they're pretty hard to tell apart.

Cat 5 ethernet cables should normally be made with solid-core cable, and 
you'll probably find that your Cat 5e stuff is also.  The stranded stuff 
is usually of the "silver satin" variety and is Cat 3 rated, usually 
used for analog voice.  However, when you go to your local supply store, 
note on the box of RJ45's if it says "stranded connector" anywhere on 
it, run away... I once cleaned up a site that used stranded connectors 
on hundreds of cables on solid-core wire.  Unexplained collisions, 
time-outs, CRC errors (big hint here... CABLE PROBLEM!), etc... on a 
whim I grabbed a handful of good quality RJ45 connectors and recrimped 
20 or so workstations.  The problems cleared up on that segment 
IMMEDIATELY.  Of course, the bad news was that we had hundreds more to 
do, and we found that DS-1/T-1 cables at the site had the same problem.

Someone simply had a box of 200 Amphenol stranded cable RJ45's and 
didn't know the difference... Sigh.  So after that lovely experience, I 
always make sure to mention it.

(The stranded stuff has points to PUNCTURE the strands of the wire and 
go through it.  The solid core stuff, GRABS the outsides of the wire 
while cutting through the insulation.  If you try to PUNCTURE solid core 
wire, the teeth on the tiny little blade on the inside of the connector 
slice through either the left or the right side of the insulation and 
only touch one side of the wire, not making firm contact.)

Some manufacturers have gone to a style that supposedly works equally 
well on either type of wire.  It has teeth on the miniature blades, and 
the blades can also split in half and surround the wire, like the 
solid-core connectors.  IMHO, these connectors suck.  They're a 
compromise and it's better to run to Graybar and buy a box of the proper 
ones if you're doing professional cabling.

Get an Amphenol crimper and a box of solid-core Ampenol RJ-45's.  I have 
put together thousands of these in multiple data centers over the years, 
and done properly they are never going to fail or cause network errors 
unless yanked apart by force (tripping over the cable while it's plugged 
in).

Let's see what else...?  Try not to cut away too much of the outer cover 
on the cable, leave enough that the outer cover is crimped into the 
connector for strain relief.  Lots of cables I've seen done by hand rely 
on the teeth of the RJ45 pins to hold the entire weight of the cable and 
these will flex and eventually fail.  There's a ridge on the back side 
of the connector that will grab the outer insulation of the cable and 
hold it with pressure for strain-relief.  In addition, leaving too much 
exposed individual wire(s) means that the twists necessary for 
cross-talk elimination are no longer there for the last inch of the 
cable, and many cables like this will work fine, but will NOT pass Cat 
5e or higher cross-talk tests on an analyzer.  Only expose as much of 
the individual wires as necessary to push them up into the RJ45.

Have fun cabling... there's definitely a difference between doing it 
right and just slapping a quick cross-over together to get a machine 
online.  At home it doesn't matter really.  Unless you're wiring the 
whole house at once or something.  :-)  Take your time, and test your 
cables.

Nate, nate at natetech.com