I am running a FRITZ!Box 6430 Cable as a cable modem with a TP-Link Archer C7 v5 running OpenWrt 19.07.2 directly attached via LAN.
The FRITZ!Box is using the 192.168.0.0/24 net, while the Archer is using the 192.168.1.0/24 net.
The FRITZ!Box can also act as a SIP telephony provider. I have configured some VOIP numbers into the modem and can make outgoing calls and receive incoming calls when directly attached to the FRITZ!Box via WIFI (e.g. using MicroSIP under Windows). However I am not able at the moment to configure the firewall on the Archer C7 in a way to forward the SIP connection between the internal network and the modem.
- When making an outgoing call, the receiving phone does ring, but there is no sound on either side.
- An incoming call well show as busy.
I have turned on firewall logging for both the LAN and WAN zones, and can see some packets being rejected, but the Source and Destination Ports do not seem to match up with the ports provided in the documentation of the modem (5060 and 7078-7109).
I am also not too sure about what mechanism I should use to forward the traffic through the firewall. As I am trying to connect two internal networks through the firewall, I think I sould be using traffic rules, but I am not too sure about that.