Fixed IP ; /etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address 192.168.15.22
        netmask 255.255.255.0
        network 192.168.15.0
        broadcast 192.168.15.255
        gateway 192.168.15.1


auto eth0:1
iface eth0:1 inet static
        address 192.168.15.42
        netmask 255.255.255.0
        network 192.168.15.0
        broadcast 192.168.15.255
        gateway 192.168.15.1

auto eth0:2
iface eth0:2 inet static
        address 192.168.16.42
        netmask 255.255.255.0
        network 192.168.16.0
        broadcast 192.168.16.255
        gateway 192.168.15.1