NDP for IPv6

IPv6 Neighbor Discovery Protocol (NDP) allows different nodes on the same link to advertise their existence to their neighbors and to learn about the existence of their neighbors. Routers and hosts (nodes) use neighbor discovery (ND) messages to determine the link-layer addresses of neighbors that reside on attached links and to overwrite invalid cache entries. Hosts also use neighbor discovery to find neighboring routers that can forward packets on their behalf. In addition, nodes use neighbor discovery to actively track the ability to reach neighbors. When a router (or the path to a router) fails, nodes actively search for alternatives to reach the destination.