Basically what the title says. Here’s the thing: It’s a solved problem. NAT already took care of this via RFC 1631. While initially presented as a temporary fix, anyone who thinks it’s going anywhere at this point is simply wrong.

And then there are the downsides of IPv6:

  • Not all legacy equipment likes IPv6. Yes, there’s a lot of it out there.
  • “Nobody” remembers an IPv6 address. I know my IPv4 address, and I’m sure many others do too. Do you know your IPv6 address, though?
  • Everything already supports IPv4
  • For IPv6 to fully replace IPv4, practically everything needs to move over. De facto standards don’t change very easily. There’s a reason why QWERTY keyboards, ASCII character tables, and E-mail are still around, despite alternatives technically being “better”.
  • Dealing with dual network stacks in the interim is annoying.

Sure, IPv6 is nice and all. But as an addition rather than as a replacement. I’ve disabled it by default for the past 10 years, as it tends to clutter up my ifconfig overview, and I’ve had no ill effects.

Source: Network engineer.