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 From:  Chris Buechler <cbuechler at gmail dot com>
 To:  M0n0wall <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] No carrier for WAN
 Date:  Sun, 12 Sep 2004 18:28:34 -0400
On Sun, 12 Sep 2004 14:18:40 -0700 (PDT), Fred Wright <fw at well dot com> wrote:
> On Tue, 7 Sep 2004, Chris Buechler wrote:
> > This is an excellent point that I was thinking about earlier.  Even
> > with present auto-negotiation, forcing speed and duplex is preferred
> > by many, including myself.
> I certainly wouldn't offer that advice in general.  I've encountered
> *multiple* occasions where people screwed things up by overriding
> autonegotiation and not setting things consistently.  And many people
> don't realize that the *switch* is the peer for this purpose.  Meanwhile,
> I've *never* seen autonegotiation get it wrong (other than the usual screw
> where the *lack* of autonegotiation on a 10BaseT station keeps its
> full-duplex capability from being usable with commodity switches).

I've seen it more times than I can count, but it's generally on older
equipment (I've seen a ton of 10/100 hubs that are notorious for
this), and ultra cheap switches.  I generally use Cisco switches, and
have never seen them have a problem with it.  I let all my gear
autonegotiate and it works fine.

I'll almost always force on a hub (on servers), because I've gone back
to clients way too many times to force half duplex when the machine
keeps setting itself to full, which significantly slows down network
performance due to all the collisions and retransmittals.  Generally
this has been a combo of new machines on old network equipment.

But yeah, you're right in that it's not a good idea to force it if
your network equipment doesn't have problems autonegotiating.  I
didn't mean to imply that you should always do it.  No sense in
increasing maintenance requirements on your network if it's
unnecessary.  In the situations that I've done it, it couldn't be set
on the switch or hub (unmanaged equipment) so changing the port the
device is plugged into would have no effect.