James Sweet wrote:

CJT wrote:

P. Thompson wrote:

On Sun, 6 Nov 2005, CJT wrote:

CJT wrote:

Geoffrey S. Mendelson wrote:

In article , CJT wrote:

You sure about that? My recollection is that Gigabit uses all 8.






I'll check, I've don't think so, but occasionaly I'm wrong. :-)


I Google'd for it, and this is the first reference I found. But I'm
fairly certain I've read it elsewhere, too, including in a textbook
on networking:

http://www.hardwaresecrets.com/article/231/2


FWIW, here's a cite with a little more impressive credentials:

http://www.cisco.com/en/US/tech/tk38...080091a86.html


Figure 7 of the cisco site shows all four pairs in use.




I can say with certainty from experience that 10bt uses only two of the
pairs, but 100bt and gigabit both use all four pairs. You have to make
sure you use both wires from the same pair for each set of signals too,
if you mix and match it doesn't work for 100 or gig, but 10 is slow
enough that it doesn't seem to matter for short runs.

I believe 100 uses only the same two pairs as 10. Only when you
move to gigabit are all 4 pairs used. Refer to the pages cited.
My understanding is that all four pairs must be present anyway,
in order for a cable to meet specs (I suspect that's to maintain
distances within the bundle, which could affect crosstalk). But
for 10/100, only half the wires are connected to anything.

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