[c-nsp] Ethernet Interfaces Speed and Duplex - Force or Auto

[Charles Mills]

That's ok Jeff.

I remember 15+ years ago when the advent of switching came upon us
that with such an eclectic cache of network cards and manufacturers
thereof that nobody seemed to be able to "get it right".
Autonegotiation was a path to trouble especially on big networks and
we did the same thing.  Now...hardly ever get a duplex mismatch unless
the cabling is substandard or there are other physical layer problems.


On Fri, May 21, 2010 at 1:07 PM, Jeff Wojciechowski
<Jeff.Wojciechowski at midlandpaper.com> wrote:
> Gert-
>
> I have done most of my learning this century so I am still somewhat green - hence my post - and I have learned much by picking the brains of vetrans.
>
> (If I had a penny for every queston I've asked LOL)
>
> Thanks,
>
> -Jeff
>
> Sent from Midland Paper Company's - BB Server
>
> ----- Original Message -----
> From: Gert Doering <gert at greenie.muc.de>
> To: Jeff Wojciechowski
> Cc: cisco-nsp at puck.nether.net <cisco-nsp at puck.nether.net>
> Sent: Fri May 21 11:57:54 2010
> Subject: Re: [c-nsp] Ethernet Interfaces Speed and Duplex - Force or Auto
>
> Hi,
>
> On Thu, May 20, 2010 at 02:18:34PM -0500, Jeff Wojciechowski wrote:
>> Curious what other network admins are doing out there for Ethernet
>> interfaces as far as speed and duplex settings - weather to specify
>> or to leave them auto negotiate.
>
> Since this is 2010, we default to "auto".  The amount of gear that makes
> problems in funny ways has been much lower with "auto" than with fixed
> setting for the last decade or so...
>
> Of course there are exceptions, most notably the 7200 FE ports that just
> don't *do* autoneg.  So for those, of course, the other end needs to be
> configured to manual/100/full.  Some carriers also insist in running their
> equipment in fixed-config mode (and inevitably get it wrong for the first
> few configuration tries).
>
> Unfortunately, there's still lot of admin folks around that have learned
> in the last century that "autoneg just doesn't work", so they go around and
> configure everything for 100/full - and then someone swaps some other gear,
> defaults to auto, boom, duplex mismatch, packet loss, nastiness.
>
> (For GigE on fiber, autoneg is good because it provides unidirectional
> link detection right away, which is something you *want* - but that's
> a different can of worms)
>
> gert
> --
> USENET is *not* the non-clickable part of WWW!
>                                                           //www.muc.de/~gert/
> Gert Doering - Munich, Germany                             gert at greenie.muc.de
> fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
>
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