James Carlson wrote:
> Sowmini.Varadhan at Sun.COM writes:
>
>> Let me ask the question another way: by setting speed and duplex separately,
>> is it actually possible to hit a permutation that would not happen
>> with the predefined <speed>{f,h}dx definition?
>>
>
> Yes. Half-duplex above 100Mbps gets pretty strange, and I suspect
> many (perhaps most) adapters don't support it. See 802.3-2002 section
> 4.1.2.1.1, 4.2.3.4, and 4.2.9. It's definitely a case of "so, remind
> me, just what problem was it you were solving .... ?"
>
>
The 10G spec finally did away with half duplex mode. 10GBaseT adapters
will probably lack support for half-duplex even when negotiating for
slower speeds (1G).
I _think_ most 1G copper adapters support half-duplex, at least when
running at 100Mbps or slower.
Half duplex is useful for debugging (the ability to insert a hub in the
middle), but a lot of 1G switches now (managed or web-managed) support
port mirroring which can achieve the same thing without having to resort
to half-duplex.
-- Garrett
