Re: Fix for kern/20700

[David Laight <david%l8s.co.uk@localhost>]

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