I have seen numerous problems with auto-negotiate myself. Usually it's a
problem between the NIC and the switch port. I've found a simple test is to
FTP some fairly good sized files back and forth to see what kind of
throughput you get. In one particular case I went to en environment where
TSM backups were seeing a network throughput of 600-1000K/sec.. this was
horrible as I was used to seeing 4000-5000K/sec.. Backups were running well
into the day.. something was seriously amiss. After doing some sniffing (we
were seeing lots of runt packets which was unusual), FTP xfer tests (which
were also bad) and moving ports around on the switch (initially we thought
the Cisco switch planer itself was bad, because when using a different older
switch the problem disappeared), I suggested forcing one of the NT boxes to
full duplex 100Mbps instead of auto-negotiate (I routinely force AIX boxes
to full duplex 100Mbps these days so the TSM server was already set that way
and we noticed that port behaved better then the others). That fixed it so
we forced them all to that setting..  Now that environment is the fastest
I've seen ranging from 6000K/sec to over 10000K/sec during TSM backups.. all
from that change.

But that was a bit unusual and extreme. I've definetly seen AIX boxes in
general be a lot happier when forced to Full Duplex 100Mbps..

So the answer is.. "it depends?"..

Gerald Wichmann
RS Engineer
Sansia System Solutions
408-844-8893 work
408-844-9801 fax