H3C S5500-SI Series Operation Manual page 10

Operation Manual – IPv6
H3C S5500-SI Series Ethernet Switches
II. 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.
III. 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 other nodes (similar to the
gratuitous ARP function of IPv4). DAD is accomplished through NS and NA messages.
Figure 1-3
Figure 1-4 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.
2) If node B uses this IPv6 address, node B returns an NA message. The NA
message contains the IPv6 address of node B.
3) 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.
IV. Router/prefix discovery and address autoconfiguration
Router/prefix discovery means that a node locates the neighboring routers, and learns
the prefix of the network where the host is located, and other configuration parameters
from the received RA message.
Stateless address autoconfiguration means that a node automatically configures an
IPv6 address according to the information obtained through router/prefix discovery.
shows the DAD procedure.
Chapter 1 IPv6 Basics Configuration
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