Force the speed and duplex of a Linux ethernet interface

Using mii-tool, the speed and duplex of an ethernet interface can be set manually.

You must set both the speed and duplex at the same time (it is not possible to autonegotiate only one). Typical combinations are:

100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD

To set 100 Mbps and full duplex on interface eth0, for example, use:

mii-tool -F 100baseTx-FD eth0

courtesy http://www.tech-recipes.com/rx/26/force-the-speed-and-duplex-of-a-linux-ethernet-interface/