Open the Terminal application. To do this, click Finder > Applications > Utilities > Terminal.app. Or alternatively you can click on Launcher and type Terminal in the search bar.

When Terminal.app is open, type the following command: netstat -nr | grep default


This will output the following:


joe$ netstat -nr | grep default


default 192.168.1.1 UGSc 50 46 en1


In this example, 192.168.1.1 is your default gateway (router) IP address.

192.168.l.l