Which statement best describes the content of an ARP reply?

• A. IP is at MAC
• B. MAC is at IP
• C. ARP reply indicates the IP address is unreachable
• D. ARP replies contain encrypted data

Answer: (A)

ARP maps IP addresses to MAC addresses on a local network. A host asks for the MAC corresponding to a specific IP, and the ARP reply provides that MAC, effectively saying that the IP address is at that MAC. That is why the statement describing the content as “IP is at MAC” is the best fit. The other ideas don’t match ARP’s purpose: ARP replies don’t indicate whether an IP is reachable, they don’t carry encrypted data, and saying “MAC is at IP” reverses the direction of the mapping that ARP provides.