Stateless address autoconfiguration

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

Stateless Address Autoconfiguration is an IPv6 mechanism by which a host generates its own address and obtains network configuration without a centralized address-assignment server.

Stateless Address Autoconfiguration (SLAAC) lets an IPv6 host generate its own address and learn network information, such as the default gateway, without a central address-assignment server. section 21.1.3

SLAAC uses NDP router discovery in this sequence:

• The host sends a Router Solicitation (RS) to the all-routers multicast address ff02::2. section 21.1.3
• A router returns, or periodically sends, a Router Advertisement (RA), typically to ff02::1. section 21.1.3
• The host combines the advertised prefix with a Modified EUI-64 interface identifier to form its IPv6 address. section 21.4

Cisco IOS configuration

On a Cisco router interface, configure ipv6 address autoconfig. The router sends an RS, receives an RA containing a prefix such as 2001:db8::/64, and generates its address automatically. Cisco IOS uses Modified EUI-64; some operating systems randomly generate the interface portion. section 21.1.3

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-message-and-generation sequence from interface configuration through RS, RA, and the completed IPv6 address. section 21.1.3

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

How deep it goes

Explains RS, RA, prefix learning, and EUI-64 address formation, while contrasting SLAAC with DHCP.

Examples

Uses Cisco IOS configuration, an R2-to-R1 discovery exchange, and the advertised prefix 2001:db8::/64.

What you can do after

Apply it via Cisco IOS using ipv6 address autoconfig to learn a prefix and generate an IPv6 address.

How it connects

Connects IPv6 Neighbor Discovery, Router Solicitation, Router Advertisement, Modified EUI-64, and DHCP.

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Related concepts

• eui-64 keyworduses · The eui-64 keyword is a Cisco IOS interface-addressing keyword that requests automatic generation of an IPv6 interface identifier from the interface MAC address.
• IPv6produces · IPv6 is the sixth version of the Internet Protocol, using 128-bit network addresses for packet-based communication.
• Neighbor Discovery Protocoluses · 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.