Terms Simple

Terms Detailed

Address Resolution Protocol (ARP) is a data link layer/network layer protocol used to convert an IP address into a physical address (called a Data Link Control (DLC) address), such as an Ethernet's MAC address. A host wishing to obtain a MAC address broadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its MAC address
Reverse ARP (RARP) is used by a host to discover its IP address. In this case, the host broadcasts its MAC address and a RARP server replies with the host's IP address

ARP Type	Description	Use Case
Proxy ARP	allows the host to answer ARP requests in place of the actual host	used by routers to register for traffic to be forwarded between hosts within the same subnet address but on different links
Gratuitous ARP	A Gratuitous ARP is an ARP Response that was not prompted by an ARP Request. The Gratuitous ARP is sent as a broadcast, as a way for a node to announce or update its IP to MAC mapping to the entire network	used to determine if the address is already in use used to update the cache entries of other hosts on the same links (e.g. in case of a change of hardware address)