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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Control Message Protocol (ICMP/ICMPv4 and ICMPv6)                 9  ICMP Message Types and Formats                      9  ICMP Version 6 (ICMPv6) Informational Message Types and Formats

ICMPv6 Router Advertisement and Router Solicitation Messages 1 2 3 4 ICMPv6 Redirect Messages

The previous topic described the Router Advertisement and Router Solicitation messages, which are used to facilitate host-router discovery functions as part of the IPv6 Neighbor Discovery (ND) protocol. The other main group of tasks for which ND is responsible relates to the exchange of information between neighboring hosts on the same network. I call these host-host communication or host-host discovery functions.

Arguably, the most important additions to the Neighbor Discovery protocol are the functions that formalize the exchange of parameters, and the methods for determining the existence of neighboring hosts. These tasks include the new method of address resolution in IPv6, as well the processes of next-hop determination and neighbor unreachability detection. They require the use of two ICMPv6 messages: the Neighbor Solicitation message and the Neighbor Advertisement message.

The Neighbor Solicitation message allows a device to check that a neighbor exists and is reachable, and to initiate address resolution. The Neighbor Advertisement message confirms the existence of a host or router, and also provides layer-two address information when needed. As you can see, these two messages are comparable to the Router Advertisement and Router Solicitation messages, but are used differently and include different parameters.

ICMPv6 Router Advertisement and Router Solicitation Messages 1 2 3 4 ICMPv6 Redirect Messages