Dual stacks enable a host to send IPv4 and IPv6 traffic. Dualstack devices are configured with an IPv4 address and an IPv6 address; thus a dualstack device can communicate directly with both IPv4 devices and IPv6 devices without requiring protocol translation. However, a network infrastructure capable of routing both IPv4 and IPv6 traffic is required.

Dual stacks alone do not enable a host to pass IPv4 traffic over an IPv6only network. A tunneling method must be implemented for IPv4 traffic to be passed over an IPv6only network. The implemented tunneling method should encapsulate an IPv4 packet inside an IPv6 header, thereby allowing the packet to travel across an IPv6 network. Because routers on the IPv6only network recognize only the IPv6 header information, the IPv4 packet is carried as the data payload of the IPv6 packet. Similarly, dual stacks alone do not enable a host to pass IPv6 traffic over an IPv4only network. The 6to4 tunneling method is one method that is used to pass IPv6 traffic over an IPv4only network. The 6to4 tunneling method is the reverse of the 4to6 tunneling method; it encapsulates an IPv6 packet inside an IPv4 header.

Network Address Translation 64 (NAT64), not dual stacks, enables an IPv4only host to communicate with an IPv6only host and enables an IPv6only host to communicate with an IPv4only host. NAT64 translates IPv4 packets to IPv6 packets and translates IPv6 packets to IPv4 packets. However, a NAT64 router must contain address mappings so that the router can correctly translate IPv4 and IPv6 addresses. NAT64 supports stateless and stateful address translation. When performing stateless translation, NAT64 uses algorithms to create a onetoone relationship between IPv6 addresses on the inside network and IPv4 addresses on the outside network. When performing stateful translation, NAT64 maps multiple IPv6 addresses to a single IPv4 address and keeps track of the state of each connection. Static mappings can also be applied manually.