NDP (Neighbor Discovery Protocol)
Neighbor Discovery Protocol (NDP), defined in RFC 4861, is IPv6's replacement for several separate IPv4 mechanisms -- ARP, ICMP router discovery, and ICMP redirects -- combined into one set of ICMPv6 message types. Neighbor Solicitation and Neighbor Advertisement resolve a neighbor's IPv6 address to its MAC address, the role ARP plays on IPv4 networks, while Router Solicitation and Router Advertisement let a host discover routers on its link and learn the address prefix it should use for SLAAC (RFC 4862) autoconfiguration. Because NDP messages are not authenticated by default, a host on the same local network can send forged Router or Neighbor Advertisements to redirect traffic or claim an address that is not its own, an IPv6 equivalent of ARP spoofing; SEND (Secure Neighbor Discovery, RFC 3971) exists to cryptographically protect these messages but sees limited real-world deployment.
By AdminKit team, Netbase JSC · Updated