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Router advertisement

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

A Router Advertisement is an ICMPv6 message that a router sends to announce itself and provide local network configuration information.

A Router Advertisement (RA) is an ICMPv6 type 134 message used by Neighbor Discovery Protocol (NDP) to announce routers and provide local IPv6 configuration information, including the network prefix and default gateway. section 21.1.3 section 21.1.2

Understand the RA exchange:

  • A host can send a Router Solicitation (RS), ICMPv6 type 133, to the all-routers multicast address ff02::2. section 21.1.3
  • The router replies with an RA sent typically to the all-nodes multicast address ff02::1; routers also send RAs periodically without receiving an RS. section 21.1.3
  • The host uses information from the RA to support Stateless Address Autoconfiguration (SLAAC), combining the learned prefix with an interface identifier to generate an IPv6 address. section 21.4

Cisco SLAAC sequence

After configuring R2 with ipv6 address autoconfig, R2 sends an RS. R1 returns an RA containing the prefix 2001:db8::/64. Cisco IOS combines that prefix with a Modified EUI-64 interface identifier to create R2’s IPv6 address. section 21.1.3 section 21.4

Figure 21.3 R2 uses SLAAC to generate an IPv6 address. (1) Issue the ipv6 address autoconfig command. (2) R2 sends an RS message. (3) R1 responds with an RA message. (4) R2 combines the learned prefix with a Modified EUI-64 interface ID to make its IPv6 address.

Follow the four-step diagram: configure SLAAC, send an RS, receive an RA, and combine the learned prefix with a Modified EUI-64 interface ID. section 21.1.3

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

How deep it goes
Explains message types, multicast destinations, timing, and SLAAC consequences, but does not detail every RA field.
Examples
Uses an R1–R2 exchange, ff02::2 and ff02::1 multicast addresses, and the ipv6 address autoconfig command.
What it assumes
Assumes basic IPv6 addressing while defining NDP, ICMPv6 message types, multicast destinations, and SLAAC.
What you can do after
Operate/configure IPv6 SLAAC and identify how an RA supplies the prefix used to form a host address.
How it connects
Connects Router Solicitation, NDP, ICMPv6, SLAAC, IPv6 prefixes, and Modified EUI-64.
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