System Administration Guide: IP Services
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IPv6 Neighbor Discovery Protocol Overview

IPv6 introduces the Neighbor Discovery protocol, which uses messaging as the means to handle the interaction between neighbor nodes. Neighbor nodes are IPv6 nodes that are on the same link. For example, by issuing neighbor discovery-related messages, a node can learn a neighbor's link-local address. Neighbor Discovery controls the following major activities on the IPv6 local link:

  • Router discovery – Aids hosts in locating routers on the local link.

  • Address autoconfiguration – Enables a node to automatically configure IPv6 addresses for its interfaces.

  • Prefix discovery – Enables nodes to discover the known subnet prefixes that have been allocated to a link. Nodes use prefixes to distinguish destinations that are on the local link from those destinations that are only reachable through a router.

  • Address resolution – Helps nodes to determine the link-local address of a neighbor, given only the destinations's IP address.

  • Next-hop determination – Uses an algorithm to determine the IP address of a packet recipient one hop that is beyond the local link. The next-hop can be a router or the destination node.

  • Neighbor unreachability detection – Aids nodes to determine if a neighbor is no longer reachable. For both routers and hosts, address resolution can be repeated.

  • Duplicate address detection – Enables a node to determine if an address that the node wants to use is not already in use.

  • Redirection – Enables a router to inform a host of a better first-hop node to use to reach a particular destination.

Neighbor Discovery uses the following ICMP message types for communication among nodes on a link:

  • Router solicitation

  • Router advertisement

  • Neighbor solicitation

  • Neighbor advertisement

  • Redirection

For detailed information on Neighbor Discovery messages and other Neighbor Discovery protocol topics, refer to IPv6 Neighbor Discovery Protocol. For technical information on Neighbor Discovery, see RFC 2461, Neighbor Discovery for IP Version 6 (IPv6).

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