How to set up virtual interface?

I have a CODA56 cable modem which requires any device attempting to connect to it to be on something other than the 192.168.0.x subnet - which mine is.

On my Edgerouter 4, I can get around that by telling it to masquerade any traffic coming from my LAN going to 192.168.1.1 as coming from a 192.168.1.x address.

Is there an easy way to set up a similar masquerade here, or will I have to migrate my entire LAN to 192.168.1.x?