Как-то так:
auto eth0:1
iface eth0:1 inet static
address 22.22.22.22
netmask 255.255.255.255
auto eth0:2
iface eth0:2 inet static
address 22.22.22.23
netmask 255.255.255.255
auto eth0:3
iface eth0:3 inet static
address 22.22.22.24
netmask 255.255.255.255