What Is ARP?
ARP (Address Resolution Protocol) is a network protocol used to link an IP address to a MAC address on a local network. It allows devices to find each other by translating logical addresses (IP) into physical hardware addresses (MAC) so data can be delivered correctly.
How ARP Works
When a device wants to send data to another device on the same network, it needs the target’s MAC address. The device sends an ARP request asking, “Who has this IP address?” The device with the matching IP responds with its MAC address. This information is then stored temporarily in an ARP table for future use.
Key Functions of ARP
- IP-to-MAC Mapping: Converts logical IP addresses into physical MAC addresses.
- Local Network Discovery: Helps devices identify each other within the same subnet.
- ARP Table Updating: Stores recently learned mappings for faster communication.
- Dynamic Resolution: Automatically finds the correct MAC address when needed.
Common Types of ARP Messages
- ARP Request: Broadcast asking which device owns a specific IP address.
- ARP Reply: Response containing the correct MAC address.
- Gratuitous ARP: A device announces its own IP–MAC mapping to the network.
- ARP Cache Entries: Stored mappings used to speed up future communication.
Why ARP Matters
ARP is essential for communication within local networks. Without it, devices would not know how to deliver data to the correct hardware address, making basic network operations impossible.
The Simple Takeaway
ARP is a protocol that connects IP addresses to MAC addresses, enabling devices on a local network to find each other and communicate effectively.