HA Setup -- no name resolution on backup with private physical addresses

[panachoi]

I've got my OPNSense HA cluster working 95% failover works, except that after failing over to the backup, name resolution doesn't work at all. I notice that name resolution doesn't work on the backup even when the master is running. I'm starting to suspect that the reason for this is that I'm using RFC1918 private addresses for the physical interfaces themselves (would explain why name resolution doesn't work on the backup while the master is running), but I dont know why it still doesn't work when the failover happens and the backup becomes primary. Note that everything else works in this case, I can still originate connections from the inside by using the IP address explicitly.

I would think this would be a common configuration, as many people dont have enough Public IP space to use as physical addresses on their internet interface.

Have I missed something obvious ?