[CentOS] 2 Ethernet cabling question

Bowie Bailey Bowie_Bailey at BUC.com
Wed Dec 29 15:19:30 UTC 2010


On 12/29/2010 9:52 AM, Blake Hudson wrote:
> -------- Original Message  --------
> Subject: Re: [CentOS] 2 Ethernet cabling question
> From: Raymond Lillard <ryl at sonic.net>
> To: CentOS mailing list <centos at centos.org>
> Date: Wednesday, December 29, 2010 12:36:43 AM
>> On 12/28/2010 08:01 PM, Drew wrote:
>>>> The colors do not matter.  What matters is the pairs.
>>> And every person who comes after you will curse your work because
>>> *both* the colors *and* the pairs are part of the 568A/B standard.
>>>
>>> In my shop if you tried that you'd be very quickly looking for work
>>> elsewhere. ;-)
>> Electrically it matters also.  If you want to be able to
>> have the cable usable to the full distance specified by the
>> standard, colors matter.  The reason is placement in the
>> bundle and crosstalk between the pairs.
>>
> I concur. What some people gloss over is that not all the pairs are the
> same. Take an ethernet cable apart at some length greater than a few
> inches and you will immediately see that some pairs can have twice as
> many twists as another. This results in slightly different electrical
> and delay properties for each pair - that become exaggerated at
> distance.  Bottom line, stick with the color scheme.

Now THAT, I did not know.  I've never stripped a network cable farther
than the inch or two I need in order to crimp on connectors.

And to set the record straight, I originally said that switching the
color scheme (even if you keep the matched pairs), is a bad idea because
it will come back to bite you (or someone else) when you have to do work
on the network later.  All I was saying is that it is possible to do --
not that it is a good idea.

-- 
Bowie



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