IPv6 on cellular IoT
Updated
IPv6 is the version of the Internet Protocol with 128-bit addresses, defined in RFC 8200. A mobile network can give a device an IPv4 address, an IPv6 prefix or both, depending on the session type requested; techniques such as 464XLAT (RFC 6877) let IPv6-only devices reach IPv4 services.
In practice
IPv6 removes the shortage of addresses, but each device becomes reachable worldwide unless traffic is filtered. Many IoT modules and platforms are still tested mainly with IPv4, so test both before choosing.