3Com Switch 8800 Advanced Software V5 Configuration Guide

IPv6 Overview 217
The NDP mainly provides the following functions:
Address resolution
Similar to the ARP function in IPv4, a node acquires the link-layer addresses of
neighbor nodes on the same link through NS and NA messages.
Figure 65 shows
how node A acquires the link-layer address of node B.
Figure 65 Address resolution
The address resolution procedure is as follows:
1 Node A multicasts an NS message. The source address of the NS message is the
IPv6 address of an interface of node A and the destination address is the
Neighbor advertisement (NA)
message
136 Used to respond to an NS
message.
When the link layer changes,
the local node initiates an NA
message to notify neighbor
nodes of the node
information change.
Router solicitation (RS)
message
133 After started, a host sends an
RS message to request the
router for an address prefix
and other configuration
information for the purpose
of autoconfiguration.
Router advertisement (RA)
message
134 Used to respond to an RS
message
With the RA message
suppression disabled, the
router regularly sends an RA
message containing
information such as address
prefix and flag bits
Redirect message 137 When a certain condition is
satisfied, the default gateway
sends a redirect message to
the source host so that the
host can reselect a correct
next hop router to forward
packets.
Table 21 Types and functions of ICMPv6 messages
ICMPv6 message Number Function
ICMP type = 135
Src = A
Dst = solicited-node multicast address of B
Data = link layer address of A
NS
ICMP type = 136
Src = B
Dst = A
Data = link layer address of B
NA
Host A Host B