Icmpv6

As explained in Acing the CCNA Exam: Volume 1 Fundamentals and Protocols

ICMPv6 is the IPv6-specific version of the Internet Control Message Protocol for communicating control, error, and diagnostic information.

ICMPv6 is the control and diagnostic messaging system for IPv6. Neighbor Discovery Protocol (NDP) is a component of ICMPv6 and uses its messages for address resolution, router discovery, and related functions. section 21.1.2 section 21.4

Important ICMPv6 message types include:

• Echo Request (128) and Echo Reply (129) support IPv6 ping. section 21.1.2
• Neighbor Solicitation (135) and Neighbor Advertisement (136) replace IPv4 ARP request and reply behavior. section 21.1.2 section 21.4
• Router Solicitation (133), Router Advertisement (134), and Redirect (137) support NDP router functions. section 21.1.2

IPv6 does not use broadcast for address resolution. A host sends an NS message to the neighbor’s solicited-node multicast address, and the neighbor returns a unicast NA containing its MAC address. The resulting Layer 3–Layer 2 mapping appears in the IPv6 neighbor table. section 21.1.2 section 21.4

Verify IPv6 neighbor resolution

After R1 pings 2001:db8::2, show ipv6 neighbors displays R2’s global and link-local addresses, their MAC address, REACH state, and Gi0/0 interface. section 21.1.2

Figure 21.2 An NDP exchange between two routers. R1 sends an NS message to learn R2 G0/0’s MAC address, and R2 sends an NA message in response.

Trace the NS request and NA response between two routers. section 21.1.2

How Acing the CCNA Exam: Volume 1 Fundamentals and Protocols covers it

How deep it goes

Explains message types, multicast behavior, address resolution, neighbor tables, and router discovery, but not ICMPv6 packet internals.

Examples

Uses IPv6 ping output, an NS/NA router exchange, solicited-node multicast addresses, and show ipv6 neighbors output.

What it assumes

Assumes basic IPv6 addressing and Layer 2 concepts while introducing NDP’s ARP-like address-resolution behavior.

What you can do after

Diagnose IPv6 neighbor resolution with ping and show ipv6 neighbors, then interpret NS, NA, RS, and RA roles.

How it connects

Connects ICMPv6 with NDP, IPv6, ARP, multicast, SLAAC, duplicate address detection, and IPv6 neighbor tables.

liveBookmanning.com

Read Acing the CCNA Exam: Volume 1 Fundamentals and Protocols on liveBook Get the book at manning.com

Related concepts

• Neighbor Discovery Protocolused by · Neighbor Discovery Protocol is an IPv6 protocol that resolves neighboring IPv6 addresses to link-layer addresses and supports functions such as router discovery and duplicate address detection.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 1 Fundamentals and Protocols. The section links point to the parts of the book it draws on.