What are the main components of the ARP cache and what issues arise when entries become stale or poisoned?

• A. The ARP cache stores DNS mappings.
• B. The ARP cache stores routing tables.
• C. The ARP cache stores VLAN configurations.
• D. The ARP cache stores IP-to-MAC mappings; stale or poisoned entries can cause misaddressed frames, dropped packets, or MITM risk.

Answer: (D)

The main idea is that the ARP cache holds IP-to-MAC address mappings for devices on the local network, so the switch or Ethernet frame can be delivered to the correct hardware address. When entries become stale or are poisoned, several problems can happen. A frame may be sent to the wrong device if the MAC address tied to an IP is outdated or incorrect, leading to misaddressed frames. If an entry cannot be resolved or is invalid, packets can be dropped while attempting to re-resolve the address. And with poisoned entries—where an attacker tricks the network into associating their MAC with a legitimate IP—traffic can be intercepted or altered, creating a man-in-the-middle risk. For contrast, DNS mappings are not stored in the ARP cache, ARP does not hold routing tables, and ARP is not about VLAN configurations.