[SWLUG] Interesting cabling puzzle

[Rhys Sage]

I've run across a real rum one here!

I have a long (15m) cable running from my Linux box to my PC with a
crossover at the Linux end.
The crossover is of the female socket with male plug type (RJ45). That works
fine.

I take the crossover out and put a short (0.5m) cable into the Linux box and
put a double-socket RJ45 crossover in and nothing happens. The NIC lights
don't come on. I try a different short cable (1m) and nothing happens. I try
the f/f crossover at the PC end and still nothing happens. I change the f/f
crossover and still nothing happens. I even tested the f/f crossover to see
whether it was a crossover or a straight through connection by putting the
m/f crossover on it. Still nothing happens.

I'm utterly baffled. All the cables are brand new and all the cables work.
I've been using them for about 2 months only and for a grand total over
those 2 months of maybe 12 hours.

Has anybody any ideas?
Yours,

Rhys