I need to create a 1 <> 1 connection between wwan0 and eth0

I am trying to create a device that will allow pass through from my qmi_wwan0 interface to my Ethernet port so I can send it to my router. I have tried bridging them but that did not work.

config interface 'eth_bridge'
        option proto 'dhcp'
        option type 'bridge'
        option ifname 'eth0 wwan0'

Any help would be appreciated!

Here you have a guide explaining why it does not work, and the alternatives: