In IPv4, it was possible for machines to automatically find out their IP address using BOOTP, and to have one dynamically assigned using DHCP, but these were relatively rare, and required non-trivial effort to set up. In IPv6, by contrast, automatic configuration is expected to be the norm.
The simplest (and hence most common) form of automatic configuration is stateless autoconfiguration. In this, the host generates each of its IPv6 addresses from an interface ID and a network prefix, as described above. The link-local prefix, FE80::/10 is well-known, and every interface gets an address based on it. To find out any other prefixes for a link, the host sends a router solicitation packet to the link-local all-routers broadcast address, FF02::2, and waits for router advertisement packets to come back. Router advertisements carry with them information about the IPv6 address prefixes in use on a link, and are sent out periodically by routers to ensure that everyone on the link has a valid address.
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The title of this document is:
Stateless autoconfiguration (RFC 2462)
URL:
http://www-uxsup.csx.cam.ac.uk/courses/moved.ipv6_basics/x115.html