Date: Fri, 8 Jun 2001 10:15:28 -0500 (CDT) From: Jonathan Lemon <jlemon@flugsvamp.com> To: kenm@icarz.com, stable@freebsd.org Subject: Re: auto-negotiate/auto-detect was Re: Any patch for fxp driver? Message-ID: <200106081515.f58FFSO60100@prism.flugsvamp.com> In-Reply-To: <local.mail.freebsd-stable/00c801c0f022$b7a6f360$711663cf@icarz.com> References: <local.mail.freebsd-stable/Pine.BSF.4.10.10106061527050.65039-100000@athena.uniserve.ca>
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In article <local.mail.freebsd-stable/00c801c0f022$b7a6f360$711663cf@icarz.com> you write:
>Hi Tom,
> I have noticed a problem running my Dell with fxp0: <Intel
>Pro10/100B/100+ Ethernet>. If I use use mediaopt full-duplex,
>suddenly I start losing packets sometimes with ping! I don't notice
>mush of a problem in running except that the program "netsaint" which
>pings my other servers starts telling me I am losing packets (usually
>1 of 5 is lost)! (It runs ping from a forked process, then in a shell
>(with spopen() ) . If I take out the mediaopt all runs well again
>(with just media 100baseTX) and it also works with full auto
>negotiation.
This sounds like a duplex mismatch; where the other end is using
half-duplex. If the autonegotiation only results in "100BaseTX",
without the "<full-duplex>" entry, then you are running half-duplex.
"Autoselect" is somewhat of a misnomer, it should really be "autonegotiate".
With this setting, the hardware participates in a protocol designed to
get both sides to agree on a common setting. Both ends of the link
are required to advertise settings they are capable of, performing and
then agree on the best setting.
Problems come in when:
1. One side is set for 'autonegotiate', and the other side is not.
This results in the side that is doing 'autonegotiate' basically
attempting to guess what the other side is doing, and possibly
getting it wrong.
2. Some vendors screwing up the autonegotiate protocol and not
selecting the "best" setting. A commonly seen error is where the
switch decides to use half-duplex instead of full-duplex, even if
both sides advertise they are full-duplex capable.
The bottom line is that the settings on both sides of the link should
match. If setting both sides to "auto" results in a half-duplex link,
then *both* sides should be hardwired to use full-duplex instead, assuming
of course, that the hardware is capable of this.
--
Jonathan
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