Note: With this option enabled, you need to set up the router as a VPN
client for any of the router's clients to be able to connect to the internet.
After this setting is on, the router needs to run the VPN client all the time, if
the VPN client is not running, the clients are Not Allowed to access the
Internet.
Setup
1) Choose "Internet Kill Switch".
Choose "Internet Kill Switch" from "VPN".
2) Enable "Internet Kill Switch".
Switch on the "Enable" button in the middle of the page.