Dual stack, NAT64 and the road to IPv6

In short: Dual stack runs IPv4 and IPv6 side by side, NAT64 lets IPv6-only devices reach IPv4 servers. That makes a gradual switch possible.

In more detail: IPv4 addresses are scarce, IPv6 is the solution, but not everything is migrated. Transition methods link the two worlds.

In Depth

• Dual stack: The device has both addresses. When connecting it tries both paths almost at once (“Happy Eyeballs”) and takes the faster. Common on home connections. Effort: managing and securing two networks.
• DS-Lite: The line is natively IPv6, IPv4 is tunnelled to the provider and shared there by carrier-grade NAT. Consequence: no own public IPv4, port forwarding does not work. See DynDNS and CGNAT.
• NAT64 + DNS64: A translator lets IPv6-only devices reach IPv4 targets. DNS64 invents matching IPv6 addresses for this. Mobile networks use it.
• 464XLAT: For apps hard-wired to IPv4 the device translates locally.
• Goal: IPv6-only in the network, IPv4 just as a service at the edge.
• Testing: ping -6, curl -6 and IPv6 test websites.

See also: NAT