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Re: wm(4) won't negotiate 1000-base-T with Cisco switches and won't operate with manual media settings
Hello. You're right. I think 1000-base-T half-duplex can be used,
but in practice it won't be because the standards say that in order to
establish a 1000-base-T link, you must autonegotiate, and most (all?)
1000-base-T NICs, whether they be in switches or host computers, support
full-duplex and so will support full-duplex operation. The problem I'm
looking at is that it appears our MII layer doesn't force autonegotiation
when the user requests 1000baset operations with ifconfig(8). It also
appears that our MII layer doesn't always play well with NICs which take
longer than 500MS to autonegotiate. While we do have an asynchronous method
of dealing with such NICs, I'm not entirely sure that's completely corect
either. To make matters worse, in case you've been following this saga,
it's not entirely clear to me that Cisco follows the autonegotiation
standards across its product lines. The Cisco 3750G that Manuel has been
talking to is an older product than the ME3400 I'm testing with, and I see
notes on Wikipedia which suggest that Cisco came late to the
autonegotiation standards party, which wouldn't surprise me, and which
could explain the diferences in behavior we're seeing.
More on this topic as I figure it out.
On Nov 28, 1:59pm, Mouse wrote:
} Subject: Re: wm(4) won't negotiate 1000-base-T with Cisco switches and won
} > [...], because the cisco doens't support 1000baseT HD.
} Does half-duplex gigabit even _exist_? I thought gigabit required a
} bunch of things, like auto-X and full-duplex and all four pairs, that
} slower speeds don't. Am I just confused?
} /~\ The ASCII Mouse
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