How many ICMPv6 message types are listed for NDP?

Neighbor Discovery Protocol (NDP) in ICMPv6 is essential for the operation of IPv6 networks. It is responsible for various functions, including address resolution, neighbor unreachability detection, and automatic address configuration. There are indeed four key ICMPv6 message types associated with NDP. These are:

1. Neighbor Solicitation (NS): Used by a device to discover the link-layer address of its neighbors or to verify the reachability of a neighbor.

2. Neighbor Advertisement (NA): Sent in response to a Neighbor Solicitation message to provide the requested link-layer address or to inform about the address's reachability.

3. Router Solicitation (RS): This is sent by a host to request Router Advertisements from routers on the network, essentially asking for network configuration information.

4. Router Advertisement (RA): Sent by routers to provide information about the local link, including router addresses and prefixes, which are essential for hosts to configure themselves appropriately.

While other ICMPv6 messages exist, these four are specifically employed in the operation of Neighbor Discovery, making the answer accurate in the context of NDP-related functionalities. Understanding this set of messages is crucial for anyone working with IPv6 networking