Which statement best describes Stateless Address Auto-Configuration as it relates to deriving the interface identifier?

• A. It uses DHCPv6 to derive the interface ID
• B. It uses a random 64-bit interface ID
• C. It derives the interface ID from the MAC address using EUI-64 formatting
• D. It uses the IPv6 prefix

Answer: (C)

In Stateless Address Auto-Configuration, a host learns the network prefix from Router Advertisements and then completes its IPv6 address by combining that prefix with an interface identifier. The typical way to form that interface identifier is to derive it from the device’s MAC address using the EUI-64 format. EUI-64 takes the 48-bit MAC, inserts FF:FE in the middle, and flips the universal/local bit to indicate a locally administered identifier. This produces a 64-bit IID that, when appended to the prefix, creates the full IPv6 address.

This matches the idea that SLAAC commonly relies on the MAC-derived EUI-64 for the IID. The other options don’t fit: DHCPv6 is used for stateful addressing, random IIDs are associated with privacy extensions (not the standard SLAAC method), and merely using the IPv6 prefix doesn’t specify the complete address without an IID.