# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
    address xxx.xxx.xxx.xxx/24
    gateway xxx.xxx.xxx.xxx.1

iface eth0 inet6 auto
    up   ip addr add yyy.yyy.yyy.yyy/24 dev eth0 label eth0:1
    down ip addr del yyy.yyy.yyy.yyy/24 dev eth0 label eth0:1