2 Ethernet cabling question

[Tim]

On Sat, 2010-12-25 at 06:44 -0800, S Mathias wrote:
> Q1) when cabling, is the color order important?

For 100 meg LANs, it's probably not important.  What's most important is
that a twisted pair of wires connect a data pair, and the right pairs at
each end.

For 1 gig LANs, it may be.  The pairs have different specifications, to
minimise crosstalk.  I don't know how critical it may be to use the
expected pairs.

For short patches, it's probably not so important.  If a fault appears,
you're more likely to replace the cable.  Or it's easy to check one end
against another.

For long cables, it's really a bad idea to wire cables in a
non-specified way.  If someone has to repair a cable fault by
reterminating the lead, they'll re-do it per the standard, and then find
they'll have to reterminate the other end, too.


> straight cabling:
> A side: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown
> B side: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown

The standard 568B wiring scheme, above.


> could be eg.: like this??
> A side: white-orange, brown, white-blue, green, white-green, blue, white-brown, orange
> B side: white-orange, brown, white-blue, green, white-green, blue, white-brown, orange

A badly wired ethernet lead.  The two outer wires should be a pair, not
split either side.

There's a simple graphical depiction of the wiring on this page:
http://en.wikipedia.org/wiki/10BASE-T


> Q2) again cabling.. i know what is the color order of straight and
> crossover cabling. 

Doesn't make much difference from the first question.  

A straight lead is the same on both sides, it can be either 568A or
568B, so long as both ends are the same wiring standard.  Most of the
world, apparently uses 568B, whereas Australia (allegedly) usually uses
568A.

A crossover cable has one of each on each end, e.g. 568A to 586B.

If you're making up leads, pick one standard and stick to it all the way
through all your wiring.


> BUT: what are the color orders, when i need to create physically two
> separated networks?

What are you attempting to do?  Use one cable instead of two LAN cables?
It's doable, for 10 or 100 meg LANs, as they only use half the wires.
But it's not a great idea.

When patching multiple equipment, use the appropriate cable for each.
Normally, you only use a cross-over cable when directly connecting two
PCs together.  And, perhaps, the "uplink" connectors for coupling two
routers together.  Just about everything else uses straight cables.



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