In IPv6, Duplicate Address Detection (DAD) is performed using which mechanism?

• A. DAD uses an ARP request to verify address uniqueness.
• B. DAD is not used in IPv6 addressing.
• C. DAD requires a router to confirm address availability.
• D. DAD uses a Neighbor Solicitation sent to the tentative address via the all-nodes multicast to detect duplicates.

Answer: (D)

In IPv6, Duplicate Address Detection uses the Neighbor Discovery Protocol to ensure the address is unique on the local link. When a node wants to use a new, tentative address, it sends a Neighbor Solicitation for that address. The destination for this NS is the all-nodes multicast group (FF02::1). If any other node on the link already uses that address, it will respond with a Neighbor Advertisement, signaling a duplicate and forcing the probing node to choose a different address. If there’s no response, the address is considered unique and can be assigned. This process is a part of IPv6’s ND framework, not ARP, and it does not require a router to perform.