PROXY ARP
Another protocol, called proxy ARP or promiscuous ARP allows the learning of other routes (RFC 1027). The concept is illustrated in Figure C-4. The router hides the two networks from each other. For example, if host A wishes to send traffic to host D, host A might first form an ARP message in order to obtain the physical address of host D on network Y. However, the ARP message does not reach host D. The gateway intercepts the message, performs the address resolution, and sends an ARP reply back to host A with the gateway's physical address in the ARP target hardware address field. Host A then uses the ARP response to update its ARP table and the ARP operation is complete. The example in this figure can be reversed. The hosts on network ...
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