Every device on a local network needs a way to translate an IP address into a physical MAC address before communication can begin. That’s the job of ARP (Address Resolution Protocol). This guide breaks down the complete ARP workflow, including requests, replies, ARP caching, Gratuitous ARP, Proxy ARP, packet captures, common troubleshooting techniques, and security issues such as ARP spoofing. Whether you’re studying networking fundamentals, preparing for CCNA, or just want to understand what happens behind the scenes on a LAN, this article has you covered.