PE-2650 query on full/half duplex

Tim Pickard tpickard at
Thu Oct 14 07:27:01 CDT 2004

Hi Phil,

The effect of half duplex depends on what your switch is set to.  They need
to be at the same duplex for full effect.  It may be that the 2650 is
autonegotiating with the switch for half duplex.  Do you have a specific
reason to run at half duplex rather than full?  My Cisco switches seem to
autoneg at half by default and I set them to full.

To force settings on the ethernet controllers you would edit the
/etc/modules.conf file.

Mine looks like:
alias eth0 bcm5700
alias eth1 bcm5700
options bcm5700 line_speed=1000,1000 auto_speed=0,0 full_duplex=1,1

I am using the Broadcom drivers currently instead of the tg3.  I will give
the tg3 a try when I apply the recent RedHat update.  I believe the tg3
parameters for the modules.conf options are different.   You may find them
in the list archive.

Hope this helps.


Tim Pickard
Systems Support Analyst and Administrator
40 Salem Street
Lynnfield, MA  01940
tpickard at

-----Original Message-----
From: linux-poweredge-admin at
[mailto:linux-poweredge-admin at]On Behalf Of
phil_galligan at
Sent: Thursday, October 14, 2004 7:52 AM
To: linux-poweredge at
Subject: PE-2650 query on full/half duplex

Hi All

DELL PE.2650
RedHat Enterprise_ES_ver_3.0
Acting WebServer.

issuing the command [dmesg] to the server informs me that eth0 is running
on half duplex

tg3: eth0: Link is up at 100 Mbps, half duplex.
tg3: eth0: Flow control is off for TX and off for RX.

I don't feel too worried about this (ie. Link is up at 100 Mbps), but for a
number of reasons, it has been questioned.

I've investigated a number of ways on how to force full duplex at startup,
but I'm not confident that any rewards will be reaped.
Is this something I need to worry about?

Many Thanks.

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