My ISP allows two dynamic IP addresses. With a Linux router I was able to grab two DHCP leases from the modem using the connected ethernet device and a pseudo ethernet device configured on top of the physical device.
Is there some way to accomplish the same thing with OPNsense? I read the docs on Interfaces but didn't see anything that looked relevant. I suppose I could use a switch to connect two physical or vlan interfaces to the modem, but if I can accomplish this without eating more physical interfaces that would be my preference.
I don't think there's any way to do it dynamically. You could get static IPs and use a /31 notation.