3Com Switch 8800 Advanced Software V5 Configuration Guide

218 CHAPTER 23: IPV6 BASICS CONFIGURATION
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 corresponds to the solicited-node multicast address. If yes, node B
unicasts an NA message containing its link-layer address.
3 Node A acquires the link-layer address of node B from the NA message. After that,
node A and node B can communicate.
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 other nodes (similar to
the gratuitous ARP function of IPv4). DAD is accomplished through NS and NA
messages.
Figure 65 shows the DAD procedure.
Figure 66 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.
Router/prefix discovery and address autoconfiguration
Router/prefix discovery means that a host 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.
ICMP type = 135
Src = ::
Dst = FF02::1:FF00:1
Data = 2000::1
NS
ICMP type = 136
Src = 2000::1
Dst = FF02::1
Target address = 2000::1
NA
Host A Host B
2000::1