Introduction to Neighbour Discovery Protocol (NDP) and Functions of NDP

Neighbor Discovery Protocol (NDP, defined in RFC 4861) is a key protocol in IPv6. Neighbor Discovery Protocol (NDP) is based on ICMPv6 and is used to identify the relationships between different neighboring devices in an IPv6 network. The many key functions of IPv6 like IPv6 address to MAC address resolution (in IPv4, ARP is used for this), router discovery are now performed using Neighbor Discovery Protocol (NDP)

Following are the important functions of Neighbor Discovery Protocol (NDP).

IPv6 address to MAC address resolution: In IPv4, Address Resolution Protocol (ARP) is used for resolving IPv4 address to MAC address. The role of Address Resolution Protocol (ARP) in IPv4 is performed by Neighbor Discovery Protocol (NDP) in IPv6. One of the duties of Neighbor Discovery Protocol (NDP) is IPv6 address to MAC address resolution.

Discovering Routers: Neighbor Discovery Protocol (NDP) is used to automatically discover routers in an IPv6 network using Router Solicitation & Router Advertisement messages.

Discovering Network Prefixes: Neighbor Discovery Protocol (NDP) is used to automatically discover IPv6 network prefixes where the host belongs to, by using Router Solicitation & Router Advertisement messages.

Autoconfiguration of IPv6 addresses: After learning IPv6 network prefixes using Neighbor Discovery Protocol (NDP) Router Solicitation & Router Advertisement messages, IPv6 devices can autoconfigure an IPv6 address by self–generating the host part of the IPv6 address by using EUI-64 method.

DAD (Duplicate Address Detection): DAD (Duplicate Address Detection) is a Neighbor Discovery Protocol (NDP) mechanism to detect whether duplicate IPv6 addresses exist in an IPv6 network. DAD (Duplicate Address Detection) is useful, because IPv6 has many address autoconfiguration mechanisms.

Neighbor Discovery Protocol (NDP) is based on ICMPv6 protocol. Following images shows Neighbor Discovery Protocol (NDP) encapsulation.

Neighbor Discovery Protocol (NDP) uses ICMPv6 Type field values from 133 to137. Following table lists Neighbor Discovery Protocol (NDP) related ICMPv6 Type field values and their use.