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.