Address Resolution Protocol

The Address Resolution Protocol (ARP) is a network protocol used to map an IP address (Internet Protocol address) to a physical MAC (Media Access Control) address in a local network. It operates at the data link layer (Layer 2) of the OSI model. ARP is used when a device on a local network needs to communicate with another device, but only knows its IP address, not its MAC address.

When a device wants to send a packet to another device on the local network, it first checks its ARP cache to see if it already knows the MAC address corresponding to the IP address of the destination device. If the MAC address is not in the ARP cache, the device sends an ARP request to the local network asking for the MAC address corresponding to the IP address. The ARP request is broadcast to all devices on the local network. The device with the IP address specified in the ARP request replies with an ARP reply containing its MAC address. The ARP reply is sent directly to the requesting device.

Once the requesting device receives the ARP reply, it adds the IP address and MAC address to its ARP cache and uses the MAC address to send the packet to the destination device on the local network.

In summary, the Address Resolution Protocol (ARP) is a network protocol used to map an IP address to a physical MAC address in a local network. It is used when a device needs to communicate with another device on the local network but only knows the IP address of the destination device. ARP helps to ensure that packets are delivered to the correct destination on the local network.

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