IPv4overIPv6

IPv4overIPv6 refers to a transitional mechanism in which IPv4 packets are carried inside IPv6 packets. This technique enables IPv4 traffic to traverse networks that are IPv6-only or predominantly IPv6, by encapsulating each IPv4 datagram within an IPv6 envelope. The IPv6 header serves as the outer packet, while the encapsulated IPv4 packet is decapsulated at the remote endpoint to restore the original IPv4 payload.

In operation, a tunnel or translation point encapsulates an IPv4 datagram in an IPv6 packet at the source and forwards it toward a corresponding IPv6-enabled tunnel endpoint. Upon arrival, the IPv6 header is removed and the original IPv4 packet is delivered to the intended IPv4 destination. This approach preserves the IPv4 addressing and payload format, while using IPv6 transport to traverse the intermediate network.

Key considerations for IPv4overIPv6 include encapsulation overhead, the resulting MTU for tunneled paths, and the need for compatible tunnel endpoints and routing configuration. Because IPv6 routers handle the outer header, the IPv4 portion remains opaque to IPv6 devices beyond the tunnel endpoints. Security implications may involve tunneling-specific protections, such as IPsec or tunnel authentication, depending on deployment.

Relation to other transition technologies is notable: IPv4can be carried across IPv6 as a dedicated tunnel, contrasting with methods that translate between IPv4 and IPv6 on the fly (translation) or approaches that carry IPv6 over IPv4 networks. Today, IPv4overIPv6 is less common in consumer networks and is largely superseded by dual-stack deployments, NAT64/DNS64, or native IPv6 connectivity where feasible.