You will need to edit that file and change the configuration for eth0 to something like this :
Code:
auto eth0
iface eth0 inet static
address {IP-ADDRESS}
network {NETWORK-ADDRESS}
netmask {NETMASK}
broadcast {BROADCAST-ADDRESS}
gateway {IP-ADDRESS-GATEWAY}
dns-nameservers {IP-ADDRESS-DNS}
Code:
auto eth0
iface eth0 inet static
address 192.168.1.30
network 192.168.1.0
netmask 255.255.255.0
broadcast 192.168.1.255
gateway 192.168.1.1
dns-nameservers 192.168.1.1 (google dns also works)
source: http://www.linuxquestions.org/questions/linux-networking-3/static-ip-%3D-no-internet-888974/