I was going to write about ETHTOOL_OPTS a couple of months ago, but unfortunately I’m a forgetful person.
If you use Fedora Core (or some Fedora-driven distributions) which uses ifcfg-DEVNAME files in /etc/sysconfig/network-scripts/ and you wish to alter your ethernet cards’ default configuration, ETHTOOL_OPTS is basically all you need! Look no further, no need to add anything in rc.local or write your own rc scripts just to force your ethernet cards to a certain configuration (be it 100Mbps full duplex or 10Mbps half duplex). Simply add this line to your ifcfg file, e.g. for eth0, edit /etc/sysconfig/network-scripts/ifcfg-eth0 and append:
ETHTOOL_OPTS=”speed 100 duplex full autoneg off”
To put this change into effect, do service network restart.
Use mii-tool to verify whether the ethernet cards apply the new configuration.