When using manual NAT in Check Point, make sure that the ‘Merge manual proxy ARP configuration’ option is enabled under the ‘Global Properties > NAT – Network Address Translation’. See screenshot below.
Once the option above is enabled, add the proxy ARP to Gaia and then install a policy for the proxy ARP to take effect.
*** Any time a proxy ARP is added to Gaia, it will only take effect AFTER a policy has been installed on the gateways.
If a policy is installed first, and then the proxy ARP added, it still won’t work. ***