In SLAAC (Stateless Address Autoconfiguration)-only mode, what flag values does the RA (Router Advertisement) contain, and what does the host do with the information?

A=1, O=0, M=0 — the host creates its own GUA (Global Unicast Address) using the RA prefix and generates its own interface ID, with no DHCPv6 (Dynamic Host Configuration Protocol version 6) server involved.

What the host receives from the RA:

• IPv6 network prefix and prefix length (e.g., 2001:db8:acad:1::/64)
• Default gateway = router's LLA (Link-Local Address) (e.g., fe80::1)
• DNS (Domain Name System) server info (if included in the RA)
• MTU (Maximum Transmission Unit) value

What the host does:

1. Takes the /64 prefix from the RA
2. Generates a 64-bit interface ID (randomly or via EUI-64 (Extended Unique Identifier (64-bit)))
3. Combines them into a full 128-bit GUA (e.g., 2001:db8:acad:1:1de9:c66:72ee:ca8c)
4. Sets the default gateway to the router's link-local address

Tip: This is the default behavior when ipv6 unicast-routing is enabled — no additional configuration needed on the router. The host is fully self-sufficient.

Go deeper:

• RFC 4862 — IPv6 SLAAC — forming the GUA by appending an interface ID to the RA-advertised prefix.