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

[Jeff Wojciechowski]

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
-- 
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de