Which scenario describes a consequence of stale ARP cache entries?

• A. ARP cache entries automatically refresh without delay.
• B. DNS queries populate ARP cache.
• C. BGP updates populate ARP cache.
• D. Stale ARP entries can cause reachability issues.

Answer: (D)

ARP cache stores mappings from IP addresses to MAC addresses on the local network so a device can deliver frames to the correct hardware address. When those mappings become stale, the sender may reuse an old MAC or fail to find a valid station, causing frames to be misdelivered or dropped. That leads to reachability problems, especially if a device has moved or changed its MAC and the cache isn’t refreshed promptly.

DNS resolution doesn’t populate the ARP cache because DNS translates names to IPs, not MAC addresses. BGP updates are routing protocol information and have no direct role in ARP caching. ARP entries do age out and are refreshed when there’s new traffic, so they don’t automatically refresh without delay.