IPv6 clients learn more than an address
IPv6 hosts use Neighbor Discovery and Router Advertisements to learn the local prefix and router information. SLAAC can build an address without a traditional DHCPv6 address lease. Link-local addresses beginning fe80:: are required for local-link communication and control traffic.
SLAAC and DHCPv6 can cooperate
SLAAC can provide the address while DHCPv6 provides additional information such as DNS, depending on router-advertisement flags and design. Stateful DHCPv6 can track address assignments. Do not assume that IPv6 always uses the same address workflow as IPv4 DHCP.
Plan for coexistence
Dual-stack runs IPv4 and IPv6 together. Tunneling carries one protocol across infrastructure that does not yet support it. NAT64 helps IPv6-only clients reach IPv4 services. Transition mechanisms solve different compatibility problems and are not interchangeable labels.
Troubleshoot the prefix and the neighbor
Check the assigned global or unique-local prefix, default-router information, link-local reachability and neighbor discovery before blaming DNS. An IPv6 address can look valid while the prefix, route or neighbor cache is wrong.