Sometimes a server only has one network interface card. If you need it to serve both internal and external traffic, you’ll need to configure dual IPs. On Ubuntu 12.04, simply edit /etc/network/interfaces and add the following at the end:
auto eth0:0iface eth0:0 inet staticaddress 192.168.2.230netmask 255.255.255.0gateway 192.168.2.1
The key part is the eth0:0 notation. Here, eth0 represents the machine’s first network card, and the trailing 0 indicates a virtual sub-interface. To add yet another IP, you would use eth0:1, and so on. Adjust the address, netmask, and gateway parameters as needed.
Then restart the networking service:
sudo /etc/init.d/networking restart
Use ifconfig to check eth0:0:
ifconfig eth0:0
Configure Dual IPs on a Single NIC