How ARP Works

What is ARP ?

• Its is stands for Address Resolution Protocol.
• ARP associates an IP address with the physical address.
• Use to resolve IP Address to MAC addresses.
• The main Work of the ARP is to convert the 32-bit IP address to 48-bit address.

Mapping of IP Address into Mac Address

• Static Mapping
  • Table is create with logical and physical Address.
• Dynamic Mapping
  • Each time a machine knows the logical Address of Another machine.
  • it can use a protocol to find the physical address

Two Different types of APR Entries

• Dynamic :-
  • Dynamic Entry is create automatically when a device sends out a broadcast message out on the network.
  • Dynamic Entry are not permanent.
  • They are flushed out periodically.
• Static :-
  • A static Entry is where someone manually enters an IP to MAC address association using ARP Command line utility.
  • A static Entry are often use to reduce any unnecessary ARP broadcast traffic on a network.

The working of ARP protocol

ARP accepts a logical address from the IP protocol, maps the Address to the Corresponding Physical address and pass it to the data link layer.

Anytime a HOST or a Router need to find a physical Address of another Host or Router on its network , it sends an ARP Query Packet. The packet Includes the physical and IP address of the receiver. Query is broadcast to the network, when the intended recipient recognizes its IP address , it sends back an ARP response packet which contains both IP and Physical Address.

ARP Packet Format

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