Setting ethernet interface speed in /etc/network/interfaces
There is an easy way to set the network interface speed in Ubuntu 14.04: In the iface section of the /etc/network/interfaces you can add the link-speed and link-duplex parameters, to pass them to ethtool. The example below sets the link speed to 100 Mbit/sec: iface eth1 inet static address 192.168.1.120 netmask 255.255.255.0 network 192.168.1.0 link-speed 100 link-duplex full