There are five types of ND messages—Router Solicitation, Router Advertisement, Neighbor Solicitation, Neighbor Advertisement, and Redirect. You can specify various ND options in an ND message.
Router Advertisement and Router Solicitation messages facilitate host-router discovery functions. Neighbor Solicitation and Neighbor Advertisement messages facilitate exchange of information between neighboring hosts on the same network. The Redirect message is used to inform a host of a better route for sending data packets to a particular destination. All the ND message types use the Internet Control Message Protocol version 6 (ICMPv6) message structure.