On 2008-11-20, Whyzzi <[EMAIL PROTECTED]> wrote: > I didn't think there was a need for a cross-over cable. > I tossed it in there trying to be thorough.
Some chips disable auto MDI/MDI-X when autoneg is forced. in those cases you can't use a standard cable, you'll need a specially wired cable (both pairs crossed). The usual crossover cable (one pair crossed) normally used with 100BASE-TX will not work with 1000BASE-T. I don't know if this affects RTL8169 but it seems likely. The em(4) I can test easily do still do auto MDI/MDI-X after forcing the media type, but I see from the driver it's not the case with all of them. You should definitely use autonegotiation with 1000BASE-T. http://standards.ieee.org/reading/ieee/interp/IEEE802.3af-2003interp-6.pdf Most of the suggestions for routinely disabling autoneg are from 100Mb days. In some cases there was a valid reason to disable it: a Cisco switch bug combined with a bug in some FreeBSD-derived PHY drivers[0] (and possibly other bugs elsewhere) resulted in a mode being selected which the hardware couldn't support. (Neither bug alone would have caused a problem, it was only seen due to a combination of the two). Of course the exact reason didn't really become clear until later, I suspect a lot of "always force full duplex" advice was passed around in the meantime because of this. [0] see e.g. r1.22 sys/dev/mii/dcphy.c in our tree
