Network Engineer Silver - Network Autoconfiguration

IPv6 has two primary mechanisms for network autoconfiguration: Stateless Address Autoconfiguration (SLAAC) and Dynamic Host Configuration Protocol for IPv6 (DHCPv6). This section of Network Engineer Silver covers  how these work.

IPv4 nodes can completely configure using just DHCPv4. They can get a node address, the subnet mask (which in combination with the node address gives you the subnet prefix, e.g. 172.20/16), the default gateway and IPv4 addresses of DNS.

IPv6 nodes can configure a Link-Local IPv6 unicast address completely on their own. If there is a source of Router Advertisement messages, they can configure the Link-Local default gateway. If the RA message contains a Prefix Information option, then they can generate one or more Global unicast addresses. Nodes that support RFC 6106 (which currently does not include Windows) can even obtain IPv6 addresses of DNS. Nodes that don't support RFC 6106 yet can obtain the IPv6 addresses of DNS from DHCPv6 if one is present, and the Router Advertisement message advertises its presence (M flag = 1 for stateful, or M flag = 0 and O flag = 1 for stateless).

If there is no source of Router Advertisement messages, IPv6 nodes can configure everything necessary except for the default gateway address from DHCPv6. This requires disabling the Router Discovery option and enabling the Managed Address option (Windows can do this). Perhaps someday an RFC will add the ability for DHCPv6 to advertise the default gateway, like DHCPv4 does.

Currently, for Windows nodes, you will need both SLAAC (which requires a source of Router Advertisement messages) and DHCPv6 (at least stateless) to fully auto-configure network settings.