Quiz Entry - updated: 2026.07.14
What additional messages does ICMPv6 include that ICMPv4 doesn't have?
ICMPv6 adds the Neighbor Discovery Protocol messages: Router Solicitation/Advertisement (RS/RA) between a host and router, and Neighbor Solicitation/Advertisement (NS/NA) between devices — plus a redirect message.
ICMPv6 Additional Messages (Neighbor Discovery Protocol):
ICMPv6 includes four new message types as part of Neighbor Discovery Protocol (ND or NDP):
Router Discovery Messages:
| Message | Abbreviation | Purpose |
|---|---|---|
| Router Solicitation | RS | Host asks "Any routers on this link?" |
| Router Advertisement | RA | Router provides prefix, gateway info |
Neighbor Discovery Messages:
| Message | Abbreviation | Purpose |
|---|---|---|
| Neighbor Solicitation | NS | "What's the MAC for this IPv6?" (like ARP) |
| Neighbor Advertisement | NA | Response with MAC address |
RA Message Details:
- Sent by routers every 200 seconds (default)
- Also sent in response to RS messages
- Contains: prefix, prefix length, DNS, domain name
- Host using SLAAC sets default gateway to router's link-local address
Key insight: ICMPv6 ND replaces ARP (used in IPv4) for address resolution and adds router discovery functionality. ICMPv6 ND also includes a redirect message that works like the ICMPv4 redirect.
Go deeper:
RFC 4861 — Neighbor Discovery for IP version 6 (IPv6) — the spec defining RS/RA, NS/NA, and redirect messages.- Neighbor Discovery Protocol — Wikipedia — overview of the five NDP message types and the functions they replace from IPv4.