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RARP : Reverse Address Resolution Protocol

RARP : Reverse Address Resolution Protocol. Introduction. RARP (Reverse Address Resolution Protocol) It used to require the Ethernet address of the IP address.

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RARP : Reverse Address Resolution Protocol

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  1. RARP : Reverse Address Resolution Protocol

  2. Introduction • RARP (Reverse Address Resolution Protocol) • It used to require the Ethernet address of the IP address. • The principle of RARP is for the diskless system to read its unique hardware address from the interface card and send an RARP request asking for someone to reply with the diskless system’s IP address.

  3. RARP Packet Format • It is almost identical to an ARP packet. • The only differences are that the frame type is 0x8035 for an RARP request or reply, and the op field has a value of 3 for an RARP request and 4 for an RARP reply. Ethernet destination addr Ethernet Source addr frame type 6 6 2 Ethernet header hard size prot size hard type prot type op Sender Ethernet addr Sender IP addr target Ethernet addr target IP addr 2 1 1 6 4 6 4 2 2 28 byte ARP request/reply

  4. RARP Operation

  5. Encapsulation of RARP Packet

  6. RARP Server Design • RARP Servers as User Processes • The complication with an RARP server is that the server normally provides the mapping from a hardware address to an IP address for many hosts. • RARP requests are transmitted as Ethernet frames with a specific Ethernet frame type field.

  7. RARP Server Design • Multiple RARP Servers per Network • RARP requests are sent as hardware-level broadcasts. • As the number of servers increases, the network traffic increase, since every server sends an RARP reply for every RARP request. • The diskless system that sent the RARP request normally uses the first RARP reply that it receives.

  8. Summary • RARP is used by many diskless systems to obtain their IP address when bootstrapped. • The RARP packet format is nearly identical to the ARP packet. • Problems with RARP include its use of a link-layer broadcast, preventing most routers from forwarding an RARP request, and the minimal information returned. • While the RARP concept is simple, the implementation of an RARP server is system dependent.

  9. The End Thank you

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