Home » HP » HP0-Y43 » What is the role of neighbor solicitation (NS) messages in the autoconfiguration of an IPv6 address?
What is the role of neighbor solicitation (NS) messages in the autoconfiguration of an IPv6 address?
A. An IPv6 node sends an NS message to inform a node undergoing autoconfiguration that it is already using a particular address.
B. An IPv6 node sends an NS message for its tentative address to determine whether another node is using it.
C. An IPv6 node sends an NS message for the global prefix to prompt other IPv6 nodes to advertise the addresses that they are using on that prefix.
D. An IPv6 node sends an NS message to prompt an IPv6 router on the link to advertise the global prefixes associated with the link immediately.
Correct Answer: B
Explanation/Reference:
Duplicate address detection
The assignment of a unicast IPv6 address to an interface involves an internal test for the uniqueness of that address using Neighbor Solicitation and Neighbor Advertisement (ICMPv6 type 135 and 136) messages. While in the process of establishing uniqueness an address has a tentative state. The node joins the solicited-node multicast address for the tentative address (if not already done so) and sends neighbor solicitations, with the tentative address as target address and the unspecified address (::/128) as source address. The node also joins the all-hosts multicast address ff02::1, so it will be able to receive Neighbor Advertisements.
If a node receives a neighbor solicitation with its own tentative address as the target address, then that address is not unique. The same is true if the node receives a neighbor advertisement with the tentative address as the source of the advertisement. Only after having successfully established that an address is unique may it be assigned and used by an interface.
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