In IPv6, what is the role of Router Advertisements (RAs) in address configuration?

• A. RAs request DNS records from a domain name server.
• B. RAs are used to deliver multicast video streams.
• C. RAs advertise presence and IPv6 prefixes to hosts, enabling stateless autoconfiguration.
• D. RAs assign unique hostnames to devices.

Answer: (C)

Router Advertisements are ICMPv6 messages sent by routers on a local IPv6 link to announce the router’s presence and the network prefixes available on that link. This information lets hosts perform stateless autoconfiguration by combining the advertised prefix with their own interface identifier to form a local IPv6 address, without needing a DHCP server. The RA also provides the default route to reach outside networks and includes flags that tell hosts whether to use DHCPv6 for address configuration or for other config like DNS. In short, RAs enable hosts to configure addresses automatically and learn routing information from the network prefix that the router advertises. The other options describe functions not provided by Router Advertisements.