[CentOS] 2 Ethernet cabling question

m.roth at 5-cent.us m.roth at 5-cent.us
Wed Dec 29 15:32:12 UTC 2010


Bowie Bailey wrote:
> 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>
>>> 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.

What he said: even if this is at home, how sure are you that you'll
remember when, a year or two from now, someone accidently pulls the, and
you have to redo the plug?

The correct quote is not "consistancy is the bugaboo of small minds", but
rather "a *foolish* consistancy is the bugaboo of small minds" (emphasis
mine). A reasonable consistancy, and following standards and best
practices and standard practice, helps keep you from shooting yourself in
the foot.

          mark




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