Although DHCPv6 is similar to DHCPv4 in what it provides, the two protocols are independent of each other. DHCPv6 is defined in RFC 3315. There has been a lot of work done on this specification over the years as indicated by the fact that DHCPv6 RFC has the highest revision number of any Internet draft.

Stateless DHCPv6 Option (Router Advertisement and DHCPv6)

The stateless DHCPv6 option informs the client to use the information in the RA message for addressing, but additional configuration parameters are available from a DHCPv6 server.

Using the prefix and prefix length in the RA message, along with EUI-64 or a randomly generated IID, the client creates its IPv6 global unicast address.

The client will then communicate with a stateless DHCPv6 server to obtain additional information not provided in the RA message. This may be a list of DNS server IPv6 addresses, for example. This process is known as stateless DHCPv6 because the server is not maintaining any client state information (i.e., a list of available and allocated IPv6 addresses). The stateless DHCPv6 server is only providing configuration parameters for clients, not IPv6 addresses.

For stateless DHCPv6, the O flag is set to 1 and the M flag is left at the default setting of 0. The O flag value of 1 is used to inform the client that additional configuration information is available from a stateless DHCPv6 server.

To modify the RA message sent on the interface of a router to indicate stateless DHCPv6, use the following command:

Router(config-if)# ipv6 nd other-config-flag