In IPv6 autoconfiguration, how do Router Advertisements and DHCPv6 interact?

• A. Router Advertisements assign IPv6 addresses directly, while DHCPv6 only provides DNS information.
• B. Router Advertisements provide the network prefix and flags for SLAAC; DHCPv6 can supply additional information and address assignment; both can be used in concert.
• C. DHCPv6 replaces Router Advertisements entirely.
• D. Router Advertisements are used only in IPv4; DHCPv6 is used only in IPv6.

Answer: (B)

In IPv6 autoconfiguration, Router Advertisements and DHCPv6 are designed to work together, not against each other. Routers periodically send advertisements that announce a network prefix and provide a default gateway to hosts on the link. The flags in these advertisements tell hosts how to configure themselves: one flag indicates whether a DHCPv6 server should be used to obtain an address, and another flag indicates whether DHCPv6 should supply other configuration information (like DNS servers). Because of this, hosts can use SLAAC to form their own address from the advertised prefix while DHCPv6 supplies additional data, or, if the address flag is set, obtain its address from DHCPv6 and still use the advertised prefix for the network context. This combined approach lets networks choose different configurations—SLAAC for lightweight addressing, DHCPv6 for centralized address management, or a mix where DHCPv6 provides DNS and other options while SLAAC handles addressing. So the interaction is collaborative: router advertisements establish the network and gateway context, while DHCPv6 can fill in address and/or additional configuration as needed.