6. ARP and RARP: Address Translation
  • Though IP packets use IP addresses, hardware addresses must be used to actually transfer data from one computer to another.
  • Address Resolution Protocol (ARP) is used to discover what hardware address is associated with a particular IP address.
    • ARP broadcasts an IP address for it's corresponding hardware address. Therefore, ARP can only be used on networks that support broadcasting.
    • The computer that has the corresponding hardware address replys with its hardware address.
    • Every computer maintains an ARP cache that contains the result of recent ARP queries, which can be viewed with command arp -a.
  • RARP is used to query a central server to discover a computer's own IP address at boot time. RARP has been superseded by a newer protocol known as BOOTP, which provides the address-mapping function of RARP and some other features.


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