Set up: Cable modem --> HW Ethernet port on Ubuntu 16 box (eth0). OpenVPN client connection (tun0) over eth0. 2nd HW Ethernet port on Ubuntu 16 box (eth1) to hardware router.
I can set up internet sharing over eth1 and run that as a DHCP server with typical 10.42.0.0.
Assume for iptables that eth0 has 192.168.1.1, tun0 has 188.8.131.52, and eth1 has 10.42.0.1.
Is it possible to simply have all the data coming in and out of eth0 be sent to eth1, without this masquerade? That way, all data from the cable modem WAN is flowing through the Ubuntu box to the hardware router, but the hardware router can still do its NAT job without the Ubuntu box doing it in between. Is this possible?