You can see how this happens in Figure 17.2. If a Proxy ARP–enabled router receives
an ARP request for an IP address that it knows isn’t on the same subnet as the requesting
host, it will respond with an ARP reply packet to the host. The router will give its
own local MAC address—the MAC address of its interface on the host’s subnet—as the
destination MAC address for the IP address that the host is seeking to be resolved. After
receiving the destination MAC address, the host will then send all the packets to the
router, not knowing that what it sees as the destination host is really a router. The router
will then forward the packets toward the intended host.