reply at bottom

Robert Redelmeier wrote:
>> windsurferLA wrote:
>>> Location #2 ? WORKS fine when linked by home built 40? long
>>> CAT5 cable. Location #3 ? DOES NOT WORK when linked by home
>>> built 100? long CAT5 cable. ? Not only is there no communication
>>> over the link, but the lights on both routers do not even
>>> indicate a connection. YET, if at this same location #3, the
>>> 100? long cable is plugged into any one of several computers,
>>> the connection indicator lights come on immediately, and full
>>> normal network access is quickly obtained.
>
> These homebuilt cables, which wiring pattern did you use?
> T-568A or -B ? If you don't know what I'm talking about,
> it is highly likely you split a pair.
>
> Please do not complain "but the other comp works".
> Difference NICs and drivers are more error-tolerant
> and have more robust fall-backs.
>
> Electrons may be color blind, but they _do_ know
> who their dance [twist] partners are.
>
> -- Robert
>

Robert ... thanks for the hint.. the likely cause has been identified.

When you asked about T-568A or T-568B, it triggered a memory. I then
recalled that the connectors were not assembled at the same time; one
end was rebuilt because of intermittent connection problems. The
intermittent end had been the very first RJ45 connector that I had ever
assembled. I further recalled being uncertain at the time I was
rebuilding the connector whether to use the "A" or "B" configuration.

Now doubting my wiring skills, I got out my jeweler's eye loop to very
carefully look at both ends to make sure one had not be wired "A" and
the other "B." The result was not what I expected. A careful
examination of the newer end appears to reveal that the blue-white (#5)
and the green white (#3) were inadvertently interchanged at that end and
only that end.

I expect that repairing the cable will solve the problem. WHAT I FIND
SURPRISING is that the cable has worked with so many (guest's) computers
for so long that it was not until the A - B question was raised that I
thought to check the colors of the inner wires - a not so easy a task
for old eyes like mine. Obviously, there is enough cross talk between
the pairs to effect a connection with most, but not all, hardware.

Although I feel rather stupid for not spotting the wiring error earlier,
I never suspected a wiring error would be the problem. When ever I
assemble a connector, I keep a multi-colored wiring chart right in front
of me. Obviously, it was not enough to preclude the error.

Thanks for everyone's help.. Tomorrow, we try a rebuild.