The Address Resolution Protocol (ARP) is one of the quiet workhorses of IP networking. Defined in RFC 826, ARP is responsible for mapping an IP address to a physical MAC address on a local network. When a device wants to send traffic to another device on the same subnet, it broadcasts an ARP request asking, “Who has this IP?” The device with that address replies with its MAC address, allowing frames to be delivered correctly at Layer 2.
Despite being simple and decades old, ARP remains essential in Ethernet-based networks. However, it also introduces security risks such as ARP spoofing, where an attacker poisons ARP tables to intercept or redirect traffic. Modern switches and firewalls mitigate this with features like Dynamic ARP Inspection (DAI).
Even in today’s software-defined and cloud-driven environments, ARP continues to underpin basic IP communication—proof that foundational protocols still shape modern infrastructure.
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