losing 100megabit and/or full duplex setup on nics

[Jeff Davis]

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everything was set to auto (switch and card) and originally negotiated 100Mbit
Full.

the card over time eventually dropped to Half duplex


Jeff Davis
Amerada Hess Corporation
Email: work@jrdavis.net
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-----Original Message-----
From: Greg Lindahl <lindahl@cs.virginia.edu>
To: Jeff Davis <jdavis@hess.com>
Cc: beowulf@beowulf.gsfc.nasa.gov <beowulf@beowulf.gsfc.nasa.gov>;
linux-vortex-bug@cesdis1.gsfc.nasa.gov <linux-vortex-bug@cesdis1.gsfc.nasa.gov>
Date: Fri Jul 16 15:23:33 1999
Subject: Re: losing 100megabit and/or full duplex setup on nics


>> 1. TCP runs extremely slow, here is a netperf result
>
>This is completely normal in the case where the switch and the card
>disagree about half vs. full duplex.
>
>You think udp is fine, but I'd bet that if you ping with 8000 byte
>packets, you'll see horrible lossage.
>
>> here is some diag info from one system using 3com card from vortex-diag
>[...]
>> Transceiver/media interfaces available:  100baseTx 10baseT.
>> Transceiver type in use:  Autonegotiate.
>> MAC settings: half-duplex.
>
>Given that you forced the card to full-duplex, this bodes ill. You can
>also probably query the switch to find out what it thinks the link is,
>and I'll bet it says full duplex.
>
>-- greg

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