ADSM-L

Re: High Comm Wait (slow network speed?)

2002-09-13 08:59:19
Subject: Re: High Comm Wait (slow network speed?)
From: Remco Post <r.post AT SARA DOT NL>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Fri, 13 Sep 2002 14:57:50 +0200
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On vrijdag, september 13, 2002, at 02:45 , Hamish Marson wrote:
I have yet to see a server correctly detect duplex when set to
auto-negotiate with a switch. Not just Sun, but every other vendor we
have as well. In fact a few years back, even the cisco engineers didn't
rate the chances of seeing a successful suto-negotiation for duplex.
Speed is OK, but everything just seems to grab half duplex when they
should be full...


Hi,

when the switch is hard set to some setting (100FD) (especially cisco)
the server must also be hard set, when the switch sets auto-negotiation,
the server must also be set to auto-neg. I've noticed again and agian
that the switch stops doing auto-neg when set hard to one speed. I have
very good experience with both sun and ibm servers (and even pc's) doing
good auto-neg with cisco and foundry switches. When the switch is set
hard, and the host auto-detect, the host will detect speed fine (this is
_detectable_) but the host cannot _negotiate_ duplex and will do the
safest thing, half duplex, since dumb 100Mb/s hubs cannot do
negotiation... it must assume half-duplex... If cisco would be as nice
as to enable auto-negotiating for just one setting, that would help a
lot in many cases....

Setting the cisco to something hard guarantees you'll have to set the
same on the host...

- ---
Met vriendelijke groeten,

Remco Post

SARA - Stichting Academisch Rekencentrum Amsterdam    http://www.sara.nl
High Performance Computing  Tel. +31 20 592 8008    Fax. +31 20 668 3167
PGP keys at http://home.sara.nl/~remco/keys.asc

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