Combine interfaces into switch/same subnet?

[gravyface]

Have a PcEngines ALIX with 3 interfaces; want to aggregate the latter two interfaces (vr1, vr2) into one, two-port LAN switch, much like most SMB commercial routers do as an option during setup.

[jimp]

Enable the OPT1 interface, then bridge that to LAN.

You'll need a firewall rule to specifically allow DHCP, and one to allow traffic out from that subnet.