What is SLAAC and why is it useful?

SLAAC (Stateless Address Autoconfiguration) lets IPv6 hosts create their own globally routable address without any DHCP (Dynamic Host Configuration Protocol) server — using only information from router advertisements.

How SLAAC works:

• Routers periodically send ICMPv6 (Internet Control Message Protocol version 6) RA (Router Advertisement) messages (every 200 seconds by default) containing the network prefix and prefix length
• Hosts use this prefix + a self-generated interface ID to create a complete 128-bit IPv6 GUA (Global Unicast Address)
• No server tracks which addresses are assigned — hence "stateless"

Why SLAAC matters:

• Not every network has a DHCPv6 (Dynamic Host Configuration Protocol version 6) server, but every device still needs a GUA
• Simplifies network administration — zero server infrastructure needed for basic IPv6 connectivity
• Hosts can also send a RS (Router Solicitation) message to immediately request an RA instead of waiting up to 200 seconds

SLAAC deployment options:

• SLAAC only — host gets everything from the RA
• SLAAC with DHCPv6 — host creates its address via SLAAC but contacts a DHCPv6 server for additional info like DNS (Domain Name System)

Go deeper:

• RFC 4862 — IPv6 Stateless Address Autoconfiguration — the canonical SLAAC spec: self-generated addresses from router-advertised prefixes.
• Neighbor Discovery Protocol (Wikipedia) — concise overview of the NDP (Neighbor Discovery Protocol) machinery SLAAC rides on.