Chapter 2
NDP Configuration
Table of Contents
2.1 NDP Overview
Introduction to NDP
The Neighbor Discovery Protocol (
) implements the router discovery function of the
Address Resolution Protocol (
) and the Internet Control Message Protocol (
)
as well as all functions of the redirection protocol in IPv4. It also provides a neighbor
unreachability detection mechanism.
When one IPv6 node appears on the network, the other IPv6 nodes on the link that directly
connects with the node can discover the node through the neighbor discovery protocol and
can further obtain its link layer address. IPv6 nodes can also search for routers through
the neighbor discovery protocol and maintain the reachability information of the active
neighboring nodes on the path. The neighbor discovery protocol solves the interactions
between nodes on the same link.
NDP Principle
The IPv6 NDP provides a group of solutions for solving communication-related problems.
The NDP supports address resolution, that is, it can resolve the IPv6 address of one IPv6
node interface into the corresponding link layer address.
The NDP supports router discovery. A host can detect the existence of routers through
the NDP and determine the IDs of the routers willing to forward packets.
The NDP supports prefix discovery. A router can distribute prefix information through the
NDP to the other connected links.
The NDP also supports neighbor unreachability detection. A node can determine the
bidirectional reachability of peer communication entities through the NDP.
All these functions of the NDP are mostly implemented by NDP packets loaded inside
ICMPv6 packets. For this reason, the NDP defines five types of ICMPv6 packets: Router
Solicitation (RS) packets, Router Advertisement (RA) packets, Neighbor Solicitation (NS)
packets, Neighbor Advertisement (NA) packets, and redirection packets.
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