IPv6 Neighbor Discovery Protocol uses Router Advertisements and Neighbor Solicitations. Which statement accurately describes their roles in address resolution and Duplicate Address Detection?

• A. NDP uses broadcast messages to discover neighbors.
• B. Routers send Router Advertisements to announce presence and prefixes; hosts use Neighbor Solicitation for address resolution and Duplicate Address Detection.
• C. RA and NS are used for routing table synchronization between routers.
• D. NDP operates independently of ICMPv6.

Answer: (B)

The key idea is that Router Advertisements are sent by routers to announce presence and network prefixes, while hosts use Neighbor Solicitation for both address resolution and Duplicate Address Detection. Routers periodically broadcast Router Advertisements to tell nodes on the link about available prefixes and configuration flags, which helps a host configure its IPv6 address (stateless autoconfiguration) and learn how to reach the local network. When a device needs to map an IPv6 address to a hardware address, it sends a Neighbor Solicitation to the target address; the target responds with a Neighbor Advertisement that provides the link-layer address. For Duplicate Address Detection, a host that is about to use a new (tentative) IPv6 address sends a Neighbor Solicitation for that address; if no Neighbor Advertisement is received, the address is unique and can be assigned. This approach relies on ICMPv6 messages and multicast rather than broad broadcasts, and it is not about routing table synchronization between routers.