[northlandboy]

I don't work with Windows, so I don't know exactly how to add proxy ARP with it. I think with Check Point systems you can edit the local.arp file though?

It's not really about adding entries to Check Point's tables though - it's about getting the upstream router to forward those frames to your firewall, and one way of doing that is to get your OS to send out ARP replies to requests for those NAT IPs. The other (better) way is to have routes on the upstream router.