Gnome- How to Show IP Address on Panel | Ubuntu
Giplet is a simple GNOME panel applet that displays your computer’s ip address. Giplet can either display the ip address of a specified ethernet interface or the ip address the outside world sees. It can also be set to recheck every so often in case your router resets or the ip address is renewed.
In terminal run this command
sudo apt-get install giplet
Right click on Panel.
Add to Panel -> Giblet.