What is IPv6 Neighbor Discovery (ND) and what three services does it provide?
IPv6 ND is an ICMPv6 protocol that replaces ARP; its three services are address resolution (IPv6→MAC), router discovery, and redirection (better next-hop selection).
IPv6 Neighbor Discovery (ND) Protocol: Part of ICMPv6, provides similar functionality to ARP but with additional features.
Three main services:
| Service | Description |
|---|---|
| Address resolution | Maps IPv6 addresses to MAC addresses (like ARP) |
| Router discovery | Hosts discover local routers and receive addressing information |
| Redirection services | Routers inform hosts of better next-hop paths |
ND Message Types:
| Message | Abbreviation | Purpose |
|---|---|---|
| Neighbor Solicitation | NS | "Who has this IPv6? What's your MAC?" |
| Neighbor Advertisement | NA | "I have that IPv6. Here's my MAC." |
| Router Solicitation | RS | Host asks for router information |
| Router Advertisement | RA | Router provides prefix and gateway info |
| Redirect | - | Router suggests better next-hop |
Key difference from ARP: ND uses multicast instead of broadcast, reducing network overhead.
Go deeper:
-
RFC 4861 — Neighbor Discovery for IP version 6 (IPv6) — the authoritative spec defining the ND services and the NS/NA/RS/RA/Redirect message types. -
Foundations of IPv6: Neighbor Discovery Protocol (NDP) — video introduction to NDP's role and services in IPv6. -
Neighbor Discovery Protocol — Wikipedia covers the five ICMPv6 message types and how NDP replaces both ARP and ICMP router discovery.