Windows Server® 2008 TCP/IP Protocols and Services

Proxy ARP

Proxy ARP is the answering of ARP Requests on behalf of another node. As RFC 925 describes, Proxy ARP is used in situations in which a subnet is divided without the use of a router. A proxy ARP device is placed between nodes on the same subnet. The proxy ARP device is aware of which nodes are available on which segment. The proxy ARP device also answers ARP Requests and facilitates the forwarding of unicast IP packets for communication between nodes on separate segments. The existence of the proxy ARP device is transparent to the nodes on the subnet. A proxy ARP device is often physically a router device; however, it is not acting as an IP router, forwarding IP datagrams between two IP subnets. Figure 3-3 shows an example of a proxy ...