@AJC01 Have you tried removing the ISP router and connecting the ER605 directly to the internet? Some ISPs allow this, I have removed my ISP router and connected directly to the internet.

@AJC01 ok, then you need to fix that before you can set up site to site vpn. you can't have a private ip on the router. Have you tried removing the ISP router and connecting the ER605 directly to the...

@AJC01 ok, then it won't work, you have to talk to your internet provider about putting the modem in bridge mode or getting a public ip Do you have private IPs on both routers or is it just one?

AJC01 wrote at the wan-ports, i have the lan adress of the isp modem (=gateway) @AJC01 it won't work, what ip is it? does it start with 192.168.x.x or 10.x.x.x

@AJC01 no no ports should be opened. when it works you should be able to ping gateway ip from lan to lan, if you get a response then vpn is established

@AJC01 Do you have a public IP on the WAN interface of the router? You must have that on both routers or it won't work.