In which scenario will an administrator need to manually define Proxy ARP?

NAT (Network Address Translation) is a technique that modifies the IP addresses or ports of packets that pass through a security gateway. NAT can be configured in two ways: Automatic or Manual. Automatic NAT means that the NAT rules are generated automatically by the security gateway based on the NAT properties of network objects. Manual NAT means that the NAT rules are defined explicitly by the administrator in the NAT policy. Proxy ARP (Address Resolution Protocol) is a technique that allows a security gateway to answer ARP requests on behalf of other hosts. Proxy ARP is needed when a host on one network segment tries to communicate with a host on another network segment that has a different IP address than its own. In some scenarios, an administrator will need to manually define Proxy ARP for NAT to work properly. One such scenario is when they configure a Manual Static NAT which translates to an IP address that does not belong to one of the firewall’s interfaces2. References: Check Point R81 Network Address Translation Administration Guide