NAT64 and DNS64.
NAT64 is a mechanism that allows IPv6 hosts to communicate with IPv4 servers. The NAT64 server has at least one IPv4 address and a 32-bit IPv6 network segment (for example 64: ff9b :: / 96, see RFC 6052, RFC 6146). The IPv6 client constructs the destination IPv6 address using the previous 96-bit range plus the 32 bits of the IPv4 address with which it wishes to communicate, sending the packets to the resulting address. The NAT64 server then creates a NAT mapping between the IPv6 address and the IPv4 address, allowing communication. Operating principle
A simplistic NAT64 environment can be seen as a network device (a router, for example) with at least two interfaces. One of the interfaces is connected to the IPv4 network, and the other to the IPv6 network. The network will be configured so that packets from the IPv6 network to the IPv4 network are routed through this router. The router will perform all translations necessary to transfer packets from the IPv6 network to the IPv4 network, and vice versa.
The translation is not symmetric, since the IPv6 address space is much larger than that of IPv4 addresses (compare: 2 in IPv6 and 2 in IPv4), so a one-one translation is not possible. In order to perform the translation, the NAT64 computer must maintain an IPv6-to-IPv4 address mapping (that is, maintains state). This type of address mapping is statically configured by system administrators or is typically created automatically when the first IPv6 packet arrives at the NAT64 server. After this flow has been created, the packets can be passed in both directions.
In general, NAT64 is designed to be used when communications are initiated by IPv6 hosts. But there are also some mechanisms (such as static address mappings) to allow otherwise.
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