The internet still runs on two addressing systems that don’t really get along: IPv4 is the one practically everyone still has to understand, with its familiar four-number addresses, and it ran out of available addresses to hand out years ago. IPv6 is the official successor, first standardized in 1998 and updated since, and despite nearly three decades of deployment work, it’s widely used in some places and still absent or only partially implemented in many others. That leaves the internet stuck in a messy halfway house: IPv4-only in some places, IPv6-first in others, and dual-stack across the entire middle. And that’s exactly the situation nobody wanted from a replacement to IPv4.