There are protocols and technologies designed to allow IPv4 and IPv6 networks to coexist and communicate with each other.

Because IPv4 and IPv6 are fundamentally incompatible in their addressing structure and packet processing, special mechanisms are needed to ensure interoperability.

We present some of the most common:

1. Dual Stack: This is the most direct technique and consists of configuring devices and servers to operate with both IPv4 and IPv6 simultaneously. Devices with dual stack capabilities can send and receive both IPv4 and IPv6 traffic, choosing the appropriate protocol depending on the destination network.
2. Tunnels: Tunneling is a method of encapsulating IPv6 packets within IPv4 packets so that they can be transported over IPv4 networks. There are several types of tunnels, such as manually configured tunnels (e.g. GRE tunnel), 6to4, and Teredo. Each has its own uses and configurations depending on the environment and network requirements.
3. Network Address Translation – Internet Protocol (NAT-PT): NAT-PT allows translation between IPv6 and IPv4 addresses. However, this method has been considered obsolete due to its complications and limitations, being replaced by NAT64.
4. NAT64/DNS64: This technique allows IPv6-only devices to access IPv4 servers. NAT64 translates the IPv6 addresses of devices to IPv4 when you need to access resources only available in IPv4. DNS64 is a mechanism that synthesizes AAAA (IPv6) records from A (IPv4) records so that IPv6 devices can understand and use IPv4 addresses.

These technologies ensure that, although IPv4 and IPv6 cannot communicate directly without intervention, devices and networks operating on any version of the IP protocol can coexist and communicate effectively while the global transition to IPv6 takes place.