1-7duplication address detection is accomplished through NS and NA messages. Figure 1-4 shows theduplicate address detection procedure.Figure 1-4 Duplicate address detectionThe duplicate address detection procedure is as follows:2) Node A sends an NS message whose source address is the unassigned address :: and thedestination address is the corresponding solicited-node multicast address of the IPv6 address tobe detected. The NS message also contains the IPv6 address.3) If node B uses this IPv6 address, node B returns an NA message. The NA message contains theIPv6 address of node B.4) Node A learns that the IPv6 address is being used by node B after receiving the NA message fromnode B. Otherwise, node B is not using the IPv6 address and node A can use it.Introduction to ND SnoopingAmong the S3100 series Ethernet switches, only the S3100-EI series support ND snooping.The ND snooping feature is used in Layer 2 switching networks. It creates ND snooping entries usingNS messages.ND snooping entries are used to:z Cooperate with the ND detection function. For details about ND detection, refer to Introduction toND Detection .z Cooperate with the IPv6 filtering function. For details about IPv6 filtering, refer to Introduction toIPv6 Filtering.After you enable ND snooping on a VLAN of a device, ND packets received by the interfaces of theVLAN are redirected to the CPU. The CPU uses ND packets to create ND snooping entries comprisingsource IPv6 address, source MAC address, source VLAN, and receiving port information.The following describes how an ND snooping entry is created, updated, and aged out.1) Creating an ND snooping entryThe device uses a received DAD NS message to create an ND snooping entry.2) Updating an ND snooping entryUpon receiving an ND packet, the device searches for the corresponding entry of the source IPv6address, and then checks the ND packet information against the found entry.
