Re: Fix for kern/20700

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        Hello.  From my reading, if you don't use autonegotiation, you need to
know, and thus manually program, the duplex with the mediaopt statement
when you configure the interface for 10baseT or 100baseT use.  That's
always been true, and is true, to the best of my knowledge, on all modern
OS's.  For unmanaged switches, the best it looks like we can do is allow
users to manually configure their interfaces, which works and has worked in
the 10baset and 100baset cases for a long time.  For any speed above
100baset, we must allow the interface to use NWay autonegotiation, with the
exception of 1000-base-X interfaces.  My patch does this for 1000baseT, but
needs to restrict negotiations to that speed if requested by the user, and,
while I'm here, I probably should make it work for 10G as well, assuming
the rest of the machinery is already there.
-thanks
-Brian

On Dec 5,  6:08pm, David Laight wrote:
} Subject: Re: Fix for kern/20700
} On Sun, Dec 04, 2011 at 10:32:02PM -0800, Brian Buhrow wrote:
} >     Hello.  I think a patch which restricts autonegotiation to 1000-base-T
} > when  1000-base-T is requested will cover all the cases I'm aware of:
} > 
} > 1.  10-base-T and 10-base-T full-duplex (works with media auto and
} > hard-coded)
} > 
} > 2.  100-base-T and 100-base-T full-duplex (works with media auto and
} > hard-coded)
} 
} For 10-base-T HDX and 100-base-T HDX a hub (or end system) might only
} support 'autodetect' instead of 'autonegotiate' - which might be why
} you recollect issues with some old cisco kit.
} 
} 'Autodetect' hubs will select between 10/100M HDX based on whether
} the link test pulses are singles, or in bursts.  Any autonegotiate
} attempts will be treated by such hubs as 100M.
} 
} This all gave some 'fun' when such hubs were common, because whether
} a link worked could depend on what is was plugged into before!
} 
} FWIW the most important think to avoid is HDX/FDX mismatch.
} 
}       David
} 
} -- 
} David Laight: david%l8s.co.uk@localhost
>-- End of excerpt from David Laight