I have an ASUS N66U
I have configured the WAN interface to use a VPN Client to connect to a 3rd party VPN Server, so that all NAT LAN connected device traffic is routed through the 3rd party VPN server.
But if the 3rd party VPN server goes down, or the connection is otherwise lost or broken, the Asus N66U will route directly from the WAN connection using e.g. my ISP.
How can I stop my Asus N66U from routing any traffic on the WAN port if the VPN connection is down?
To answer my own question, in the hope that maybe it helps someone else…
So I tried
Finally I found Merlin. Merlin let me configure OpenVPN with a .ovpn file.
There is an option “Redirect Internet Traffic” you can set to “Policy Rules”
You can use CIDR notation to specify all client IPs on the subnet, e.g. 192.168.1.0/24, destination 0.0.0.0
And you can select “Block routed clients if tunnel goes down”
See also: https://www.snbforums.com/threads/vpn-what-does-redirect-internet-traffic-all-do.56145/
Also search for: killswitch