Never force full duplex.

Dan Stromberg strombrg@nis.acs.uci.edu
Fri Mar 31 13:42:01 2000


Donald Becker wrote:
> 
> On Fri, 31 Mar 2000, Cy wrote:
> 
> > I too had problems with crossovers, except that I was attempting to force
> > full duplex.  Could never get it to work.  I just let autonegotiation take
> > care of itself and I get full duplex like I wanted.
> 
> This is common enough that it is worth repeating:
> 
>       Never force full duplex.
>       Never.  No, not then.  No, it's not a secret go-faster flag.
> 
> There is only one place where forcing full duplex is needed, and that is
> when you are talking to an old or misdesigned switch that doesn't have
> autonegotiation, and you cannot change the switch configuration.  If you can
> change the switch configuration, change it back to half duplex and save
> yourself future headaches.  You probably don't see any significant
> performance improvement when using full duplex on switches without working
> autonegotiation anyway.

I'm inclined to trust you on this Don, but I'd appreciate it if you
could tell us more about the reasoning that went into this conclusion.
I'm hesitant to recommend things on authority; I much prefer to
understand (at least) a little bit about what I'm recommending.

Are you thinking that any switch that neglects autonegotiation, probably
also neglects to have a decent FD implementation?

> Read
>   http://cesdis.gsfc.nasa.gov/linux/misc/NWay.html
> for more info on N-Way autonegotiation.

I searched this URL for the string "forc" and found 0 occurences.
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