Address Resolution Protocol
ARP

    (ARP) A method for finding a host's
   Ethernet address from its Internet address.  The sender
   broadcasts an ARP packet containing the Internet address
   of another host and waits for it (or some other host) to send
   back its Ethernet address.  Each host maintains a cache of
   address translations to reduce delay and loading.  ARP allows
   the Internet address to be independent of the Ethernet address
   but it only works if all hosts support it.

   ARP is defined in RFC 826.

   The alternative for hosts that do not do ARP is constant
   mapping.

   See also proxy ARP, reverse ARP.

   (1995-03-20)