Setup kill switch for OpenVPN on Android
Make sure the VPN profile you wish to connect to is set as Default VPN from Settings tab in homescreen of App.
Enable kill switch
Navigate to Android’s Settings > Wireless & networks > VPN.
Click on gears like icon to the right of OpenVPN for Android label to enter app specific settings for VPN.
Enable/toggle Always-on VPN option to ON.
Once you have a VPN connection. Enable/toggle Block connections without VPN to ON.
Android OS will prompt you a question, tap TURN ON to finally enable your kill switch.