# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet static
        address 192.168.21.2/24
        gateway 192.168.21.1
iface eth0 inet6 static
        address fd18:76a0:3427:201::2/64
iface eth0 inet6 auto