[Bioclusters] Xserve going full duplex

Ruotti, Victor bioclusters@bioinformatics.org
Tue, 12 Aug 2003 09:13:25 -0500

I just finished setting both the switch and the Ethernet cards to 100 full
for the two xserves. I use the "manual solution", forced both the switch and
the NIC to go 100 full. It work out great! Autonegotiation just did not work
for us in this case.


Victor Ruotti
Medical College of Wisconsin

-----Original Message-----
From: andy law (RI) [mailto:andy.law@bbsrc.ac.uk]
Sent: Tuesday, August 12, 2003 4:40 AM
To: 'bioclusters@bioinformatics.org'
Subject: RE: [Bioclusters] Xserve going full duplex

Donald Becker wrote:

> That is a very bad solution.  If you must must disable autonegotiation
> because of flawed hardware, disable the broken end and allow 
> the link to
> use half duplex.
> Auto-negotiation is reliable, and failure is always because of flawed
> hardware.  In the past there were several switch vendors that didn't
> want to acknowledge problems with what they were shipping, 
> and therefore
> implied that auto-negotiation was flawed as a concept.  
> Modern products
> almost universally implement it correctly, and there is now a quiet
> restatement of recommended practices.
>   http://www.cisco.com/warp/public/473/46.html
> A quick background on autonegotiation is available at
>   http://scyld.com/expert/NWay.html
> Bottom line: Auto-negotiation works.  If you turn it off because of
> broken switches, never set the port forced-full-duplex mode.

But from reading Table 1 in the article on the cisco site, if the problem is
at the switch end, the *ONLY* way to get a 100MB connection is to manually
configure both ends. Now I'm not au-fait with the reasons to choose
half-duplex or full-duplex so I could be missing the point, but I do know
that if it comes to a choice between a 10MB link, a 100MB link with a
mismatched duplex or a working 100MB link then I'll choose the 'bad
solution' of manual configuration.



Dr. Andy Law
Head of Bioinformatics - Roslin Institute

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