IPv6

Every device on the internet needs an address it can be reached at. IPv4, the older version of the Internet Protocol, uses 32-bit addresses, providing a little over four billion possible addresses — a number the world ran short of long ago. IPv6 solves that with 128-bit addresses and an address space that is, for practical purposes, inexhaustible.

In most business networks, this barely shows up day to day, because internal devices already use private IPv4 address ranges and a single internet connection presents itself to the outside world via NAT (Network Address Translation) on behalf of all of them. That approach sidesteps the address shortage without IPv6 needing to appear on the network at all. Where IPv6 is used, it usually runs alongside IPv4 rather than replacing it.

IPv6 does matter in certain situations: very large numbers of individually addressable devices, such as bigger IoT deployments; some fiber or mobile connections that come with native IPv6 out of the box; or a specific cloud service or provider that requires IPv6 reachability. One grey area is devices on the network that do support IPv6 but for which nobody has maintained the matching firewall rules, because attention so far has only gone to IPv4.