"Do you think you have a network bottleneck that's somehow
related to your NIC's speed or other settings? If so, ethtool might
be the utility that will save the day and many painful
conversations. Ethtool is a privileged user only (root), powerful
system tool that allows you to query and change settings for your
system's ethernet cards. Using it, you can change almost every
aspect of a supported card; from the basic to the esoteric.
"If ethtool didn't ship with your distribution, pick it up at:
Ethtool's Sourceforge Site. Whether it comes installed on your
distribution or you have to install it from source, you'll find
ethtool a valuable new tool and will soon wonder how you lived
without it. You must have root or sudo access to install and use
ethtool, since it alters a system component's settings.
"You can alter the speed, duplex modes, autonegotiation, wake on
LAN (WoL) options and perform tests to name a few of the things you
can do with ethtool."