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Introduction to IPv6 Neighbor Discovery Protocol
The IPv6 Neighbor Discovery Protocol (NDP) uses five types of ICMPv6 messages to implement the
following functions:
z Address resolution
z Neighbor unreachability detection
z Duplicate address detection
z Router/prefix discovery
z Address autoconfiguration
z Redirection
Table 1-3 lists the types and functions of ICMPv6 messages used by the NDP.
Table 1-3 Types and functions of ICMPv6 messages
ICMPv6 message Function
Used to acquire the link-layer address of a
neighbor
Used to verify whether the neighbor is reachable
Neighbor solicitation (NS) message
Used to perform a duplicate address detection
Used to respond to a neighbor solicitation
message
Neighbor advertisement (NA) message
When the link layer address changes, the local
node initiates a neighbor advertisement
message to notify neighbor nodes of the change.
Router solicitation (RS) message
After started, a host sends a router solicitation
message to request the router for an address
prefix and other configuration information for the
purpose of autoconfiguration.
Used to respond to a router solicitation message
Router advertisement (RA) message
With the RA message suppression disabled, the
router regularly sends a router advertisement
message containing information such as
address prefix and flag bits.
Redirect message
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.
z The 3com switch 4500 does not support the RS, RA, or Redirect message.
z Of the above mentioned IPv6 NDP functions, 3com switches 4500 support the following three
functions: address resolution, neighbor unreachability detection, and duplicate address detection.
The subsequent sections present a detailed description of these three functions and relevant
configuration.
The NDP mainly provides the following functions: