How does IPv6 neighbor discovery function, and what are the roles of ICMPv6 messages in address resolution and duplicate address detection?

How does IPv6 neighbor discovery function, and what are the roles of ICMPv6 messages in address resolution and duplicate address detection?

• A. NDP uses ICMPv6 messages (Neighbor Solicitation and Neighbor Advertisement) to map IPv6 addresses to MACs; DAD uses NS/NA to detect duplicates; these mechanisms replace ARP for IPv6.
• B. NDP uses IPv4 ARP packets; ICMPv6 is not used.
• C. NDP uses Router Advertisements only.
• D. IPv6 uses DNS for address resolution.

Answer: (A)

IPv6 uses ICMPv6-based Neighbor Discovery to handle how devices learn about each other on the same link and how they map addresses to hardware addresses. When a device needs to contact another host on the local link, it sends a Neighbor Solicitation to the target’s solicited-node multicast address asking for the target’s MAC address. The owner of that IPv6 address responds with a Neighbor Advertisement that includes its link-layer address, allowing the requester to fill its neighbor cache and communicate at layer 2 directly. This NS/NA exchange replaces the need for ARP in IPv6, since ICMPv6 handles the address resolution process. For duplicate address detection, a host that is configuring a new IPv6 address performs a similar NS/NA exchange to its own tentative address. It sends a Neighbor Solicitation to the solicited-node multicast address for that tentative address with an unspecified source address. If another device already uses that address, it will reply with a Neighbor Advertisement, signaling a conflict. If no conflicting response is received, the address is considered unique and can be used. Other options don’t fit because IPv6 address resolution and duplicate address detection rely on ICMPv6-based Neighbor Discovery, not IPv4 ARP, not Router Advertisements alone, and not DNS for address resolution.

IPv6 uses ICMPv6-based Neighbor Discovery to handle how devices learn about each other on the same link and how they map addresses to hardware addresses. When a device needs to contact another host on the local link, it sends a Neighbor Solicitation to the target’s solicited-node multicast address asking for the target’s MAC address. The owner of that IPv6 address responds with a Neighbor Advertisement that includes its link-layer address, allowing the requester to fill its neighbor cache and communicate at layer 2 directly. This NS/NA exchange replaces the need for ARP in IPv6, since ICMPv6 handles the address resolution process.

For duplicate address detection, a host that is configuring a new IPv6 address performs a similar NS/NA exchange to its own tentative address. It sends a Neighbor Solicitation to the solicited-node multicast address for that tentative address with an unspecified source address. If another device already uses that address, it will reply with a Neighbor Advertisement, signaling a conflict. If no conflicting response is received, the address is considered unique and can be used.

Other options don’t fit because IPv6 address resolution and duplicate address detection rely on ICMPv6-based Neighbor Discovery, not IPv4 ARP, not Router Advertisements alone, and not DNS for address resolution.