I rejoiced too soon. There a problems on reboot (no network or other issues). So you are right this is an issue.
I already had PRE and POST rules to get traffic to the internal address of the container and that the container is using the correct address for outgoing traffic.
Now the issue arised as I am running a container with jitsi meet and wanted to add a SIP gateway. The point here is that the jicofo service needs to connect to the external ip of the asterisk service (on the same container) so that the external ip is visible for the connection from the outside world.
The question is how can I configure iptables in a way the I can use routed networking with this use case.
Thanks 