In other words, ARP is a protocol that can resolve an IP address to a hardware address. It broadcasts a hardware layer request, and the target device responds with the hardware address that matches the known IP address.
When a TCP/IP device needs to forward a packet to a device on the local subnet, it first looks in its own table, called an ARP cache, for an association between the IP address of the destination device on the local subnet and the same device’s MAC address.
ARP cache is an area in random access memory (RAM) where ARP keeps the IP and hardware address that have been resolved.
If ARP can found the IP and hardware addresses in ARP cache, the packet is addressed to the hardware address with no further resolution.
If no association that includes the destination IP address can be located, the device sends out an ARP broadcast that includes its own MAC and IP information as well as the IP address of the target device and a black MAC address field, which is the object of the whole operation.
All hosts on the segment receive the broadcast but only the host with specified IP address responds with its MAC address. At this point, layer 3 communication can begin.
Telecommunication protocol of ARP (address resolution protocol)
*TCP – Transmission Control Protocol
*IP - Internet Protocol
*MAC - media access control
