Which NDP messages are utilized during Duplicate Address Detection (DAD)?

Neighbor Discovery Protocol (NDP) is integral to the operation of IPv6 networks, and it includes several message types that facilitate various functions, one of which is Duplicate Address Detection (DAD). During DAD, a device wants to ensure that its intended IPv6 address is not already in use by another device on the network.

The process utilizes Neighbor Solicitation (NS) messages, which the device sends out to check for any existing address conflict. When a network device receives an NS that is directed at its own address, it is expected to respond with a Neighbor Advertisement (NA) message. If no NA is received in response to the NS, the address is considered unassigned or available for use.

In summary, the correct answer identifies that the NS and NA messages are the critical components used during DAD. The NS message probes for address conflicts, while the NA message serves as a confirmation if that address is already in use. This mechanism ensures that devices on the same link can communicate effectively and avoid address collisions that could lead to network issues.