H3C Technologies H3C S3100 Series Switches - Manual (Page 910)

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duplication address detection is accomplished through NS and NA messages. Figure 1-4 shows the
duplicate address detection procedure.
Figure 1-4 Duplicate address detection
The duplicate address detection procedure is as follows:
2) Node A sends an NS message whose source address is the unassigned address :: and the
destination address is the corresponding solicited-node multicast address of the IPv6 address to
be 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 the
IPv6 address of node B.
4) 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.
Introduction to ND Snooping
Among 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 using
NS messages.
ND snooping entries are used to:
z Cooperate with the ND detection function. For details about ND detection, refer to Introduction to
ND Detection .
z Cooperate with the IPv6 filtering function. For details about IPv6 filtering, refer to Introduction to
IPv6 Filtering .
After you enable ND snooping on a VLAN of a device, ND packets received by the interfaces of the
VLAN are redirected to the CPU. The CPU uses ND packets to create ND snooping entries comprising
source 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 entry
The device uses a received DAD NS message to create an ND snooping entry.
2) Updating an ND snooping entry
Upon receiving an ND packet, the device searches for the corresponding entry of the source IPv6
address, and then checks the ND packet information against the found entry.