You have an interface in OpenWRT with your modem IP with a wan device under it, but you’re using your modem in bridge mode using PPPOE for internet access for your clients connected to the OpenWRT router…?
Why have an interface for your modem? It’s unnecessary and redundant. It’s creating a network mask route for your modem IP to point to your OpenWRT router. Try disabling the modem interface and you should be able to get to your modem’s GUI with its IP address.
EDIT: Ahh, I see what you’re trying to do in creating an alias following that guide and that the interface IP is indeed different. Sorry, I never had this issue. My ISP allows for passthrough with DHCP set on both wan and wan6 and connecting to the modem GUI when connected to the LAN network wasn’t an issue for me.
I checked everything one more time and found my problem.
The interface ip should be 192.168.15.2 and the gateway the modem ip, 192.168.15.1
After that I managed to make it work.
Thank you guys for the tips.
LOVE