How do I add ethtool settings to a network device permanently?

ethtool can be used to set options for many types of ethernet devices. The /etc/sysconfig/network-scripts/ifcfg-ethX can have the ethtool settings added to the file so that the settings are in place whenever the device is brought up.

For example, the command :

ethtool -s eth0 speed 100 duplex full autoneg off

will set...