OpenWrt + Fritzbox 4040 behind cisco (Cable)Router


my first contribution here and at the same time my first question regarding the configuration of the Fritzbox 4040 with installed openWRT. Installation and WLAN setup went without any problems. The only problem I can't solve is that the router can't find its way to the Cisco modem on the cable connection.

A cable goes from the router to the Cisco modem at the WAN connection. There are no problems with the original Fritz software.

I can't find a solution how the WAN port could get an IP address. Only one MAC address can be recognized.

I'd be grateful for help.

I am not sure I understand the problem properly. Are you trying to manage the web interface of the modem from the hosts behind OpenWrt?