TP-Link T2600G-28MPS T2600G-28MPSUN V1 User Guide - Page 195
Neighbor Reachability Detection, Duplicate Address Detection
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After receiving the NS message, node B judges whether the destination address of the packet corresponds to the solicited-node multicast address. If yes, node B can learn the link-layer address of node A, and unicasts an NA message containing its link-layer address. 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. Node A sends an NS message whose destination address is the IPv6 address of node B. 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 Neighbor solicitation messages are used in the stateless autoconfiguration process to verify the uniqueness of unicast IPv6 addresses before the addresses are assigned to an interface. After node A acquires an IPv6 address, it will perform duplicate address detection (DAD) to determine whether the address is being used by other nodes (similar to the gratuitous ARP function of IPv4). DAD is accomplished through NS and NA messages. The DAD procedure is as follows: 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. If node B uses this IPv6 address, node B returns an NA message. The NA message contains the IPv6 address of node B. Node A learns that the IPv6 address is being used by node B after receiving the NA message from node B. Otherwise, node B is not using the IPv6 address and node A can use it. 2. IPv6 Router Advertisement Message Router advertisement (RA) messages, which have a value of 134 in the Type field of the ICMP packet header, are periodically sent out each configured interface of an IPv6 router. RA messages typically include the following information: One or more onlink IPv6 prefixes that nodes on the local link can use to automatically configure their IPv6 addresses. Lifetime information for each prefix included in the advertisement. Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed. 184