@vizi0n Gotcha, so the goal is to spoof the MAC address on a CARP event so that the ISP router, which is handing IPs out via DHCP, gives the new primary the same IP as the previous (or ideally no DHCP even has to happen again).
Not sure if there is a way to do this, nothing is immediately coming to mind, definitely not a "supported" config but I'm sure you knew that haha.
Of course pfSense does support spoofing the MAC on an interface, but I don't know of a good way without doing a LOT of custom work to program it to do so based on a CARP event trigger.
Sorry, since saying IDK isn't really that helpful lol.
P.S. sorry for late reply, was on a work trip so didn't really have time to check forum stuff.