why a standard ethernet cable worked when a patch cable didn't

Michael Torrie torriem at gmail.com
Sun Dec 9 18:27:00 MST 2012


On 12/09/2012 05:25 PM, Wade Shearer wrote:
> What's unique about that cable or about the Linsys switch that they work together?

I bet one of the pairs in the cable is bad, but not one of the the two
pairs needed for 100 Mbit/s connection.  The Cisco switch and the
airport extreme are almost certainly trying to negotiate for gigabit,
and since gigabit requires all four pairs to be good.  I'm not sure why
the switch won't drop down and negotiate for 100 Mbit when the gigabit
fails.  I could be wrong though.

I recommend you invest in a good network tester.  They aren't cheap, but
if you get one that can do wire maps and other forms of cable testing, I
think you'll find it quite handy.  I bought myself a little lanscaper,
and it has been extremely useful for my home networking projects.
Besides being able to emit a powerful tone for tracing wires, it can do
wire testing, and also test a port of a switch and determine what kind
it is, and what protocols it supports (802.1q for example), vlans, etc.
 But mostly I use it for wire maps, and for telling me how long a cable
run is.

My Lanscaper can only do 100 mbit when it comes to testing a switch or
an active connection, but that seems to be enough for me. I think the
pro version can do gigabit.  And if you're really rich there is the
Fluke version!


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