Prefix Information

Router advertisements also contain zero or more prefix information options that contain information used by stateless address autoconfiguration to generate site-local and global addresses. It should be noted that the stateless and stateful address autoconfiguration fields in router advertisements are processed independently of one another, and a host can use both stateful and stateless address autoconfiguration simultaneously. One prefix information option field, the autonomous address-configuration flag, indicates whether or not the option even applies to stateless autoconfiguration. If it does, additional option fields contain a subnet prefix with lifetime values, indicating how long addresses created from the prefix remain preferred and valid.

Because routers generate router advertisements periodically, hosts continually receive new advertisements. Hosts process the information contained in each advertisement as described above, adding to and refreshing information received in previous advertisements.