As far as I know the BRIDGe mode is not supported on this device, instead port forward/DMZ can be used.
I attached my own device to the Connect Box 3 Fiber and set its internal IP as DMZ.
Sadly not everything arrives to here, I miss IP protocol 47. The port forwarding option also not offers just TCP and UDP protocols.
How to configure this router to do proper NAT?
Any hints, suggestion help are welcome.