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