The ARP cache (Address Resolution Protocol cache) is a temporary memory table maintained by operating systems and network devices that maps IP addresses to MAC addresses. This cache enables efficient communication within local networks by translating logical IP addresses (used at the network layer) into physical MAC addresses (required for data link layer transmission). When a device needs to send data to another host on the same network, it first checks its ARP cache for the destination's MAC address, allowing immediate data delivery without additional network queries.

If no matching entry exists, the device broadcasts an ARP request to discover the target's MAC address, then stores the response in the cache with a Time-to-Live (TTL) value for automatic expiration. From a cybersecurity perspective, the ARP cache presents significant security considerations. Its trust-based operation within local network segments makes it vulnerable to attacks such as ARP spoofing or poisoning, where malicious actors can manipulate cache entries to intercept traffic, conduct man-in-the-middle attacks, or disrupt network communications. Understanding and monitoring ARP cache behavior is essential for maintaining network integrity and security.