Setting up a static IP address in Ubuntu server

• Configuration file 

$ sudo vi /etc/network/interfaces

• DHCP

auto eth0
iface eth0 inet dhcp

• Static IP

auto eth0
iface eth0 inet static
      address 192.168.1.100
      netmask 255.255.255.0
      network 192.168.1.0
      broadcast 192.168.1.255
      gateway 192.168.1.1