For the very first time i tried to selfhost a static site (lighttpd + duckdns) but I’ve failed… Is it even possible to selfhost a static site from “router 2” while i’m behind two routers? “Router 1” is from ISP and i have no possibility to change any settings except subnet, standard gateway, dhcp on/off and DMZ. -> no port forwarding. "Router 2 is Asus with port-forwarding available and i’m using an OpenVPN configuration on it (if that matters). DuckDNS could see the external ip from R2, but i couldn’t access it.
it’s fiber.
Do you have a username and password for PPP? You could replace the device with something with a SPF port
Another option is that you could turn off masquerading (NAT) on the Asus router. This may not work but if you have different IP ranges on each device theoretically it would avoid double NAT