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13-7
Figure 13-3
Address resolution
The address resolution procedure is as follows:
1) Node A multicasts an NS message. The source address of the NS message is the IPv6 address of
the sending interface of node A and the destination address is the solicited-node multicast
address of node B. The NS message contains the link-layer address of node A.
2) After receiving the NS message, node B judges whether the destination address of the packet is
its solicited-node multicast address. If yes, node B learns the link-layer address of node A, and
then unicasts an NA message containing its link-layer address.
3) Node A acquires the link-layer address of node B from the NA message.
Neighbor reachability detection
After node A acquires the link-layer address of its neighbor node B, node A can verify whether node B
is reachable according to NS and NA messages.
1) Node A sends an NS message whose destination address is the IPv6 address of node B.
2) If node A receives an NA message from node B, node A considers that node B is reachable.
Otherwise, node B is unreachable.
Duplicate address detection
After node A acquires an IPv6 address, it will perform duplicate address detection (DAD) to determine
whether the address is being used by any other node (similar to the gratuitous ARP function of IPv4).
DAD is accomplished through NS and NA messages.
Figure 13-4 shows the DAD procedure.
Figure 13-4
Duplicate address detection
The DAD procedure is as follows:
1) Node A sends an NS message whose source address is the unassigned address :: and
destination address is the corresponding solicited-node multicast address of the IPv6 address to
be detected. The NS message contains the IPv6 address.