Adicione uma pilha de linhas assim:
iface eth0 inet static
address 192.168.0.1
netmask 255.255.255.0
up ip addr add 192.168.0.2/24 dev eth0
up ip addr add 192.168.0.3/24 dev eth0
up ip addr add 192.168.0.4/24 dev eth0
up ip addr add 192.168.0.5/24 dev eth0
...