[geeks] SunOS4/IPC: Change mac

[Lionel Peterson]

As I recall, 10 Mbs uses half the pairs in Cat5, 100 Mbs uses three pairs, and
Gigabit uses all four pairs... I'm sure this is documented somewhere, but I'm
also sure I've *mostly* got it right.

Lionel

On Dec 21, 2014, at 6:13 PM, Mouse <mouse at Rodents-Montreal.ORG> wrote:

>> Now the network connection drops above a certain packet size...but
>> only now the system is in the basement.
>
>> ...I'm gonna blame my hacked-up temporary switch.
>
> Don't exclude your physical layer, such as wiring.  I have a friend
> with whom I was talking about networking.  He told me that he recently
> switched a particular piece of his house network from 10Mb to 100Mb and
> promptly started getting severe packet loss, even though he'd run CatV
> and thus should be able to get gigabit speeds out of it.
>
> It developed, later, that he had crimped the connectors himself.  This
> would not have been an issue, except that he was not aware that 8P8C
> ("RJ45") networking puts the pairs on pins 1-2, 3-6, 4-5, and 7-8; he
> had put them on 1-2, 3-4, 5-6, and 7-8.  Of course, this meant that one
> "pair" was actually using conductors from two different pairs, each of
> which had its paired conductor going unused.  Apparently 10Mb was
> forgiving enough to work under that condition at the cable length in
> use, but 100 wasn't.  Fixing the pairing made it all work well.
>
> This particular problem may not be your issue; I cite it just to point
> out that sometimes problems arise from issues with unquestioned parts
> of the setup and are thus unresolvable until those parts get
> questioned, or at least fixed _somehow_.
>
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