ARP works by broadcasting a packet to all hosts attached to an Ethernet. The packet contains the IP address the sender is interested in communicating with.
Most hosts ignore the packet.
The target machine, recognizing that the IP address in the packet matches its own, returns an answer. ARP, Bridging and Routing ARP is transparent to bridging , since bridging will propagate ARP broadcasts like any other Ethernet broadcast, and will transparently bridge the replies. A router does not propagate Ethernet broadcasts, because the router is a Network Level device, and Ethernet is a Data Link Level protocol. Therefore, an Internet host must use its routing protocols to select an appropriate router, that can be reached via Ethernet ARPs. Proxy ARP Proxy ARP is a technique that is can be used by routers to handle traffic between hosts that don't expect to use a router as described above.