[MayeulC]

NAT64 is useful to allow IPv4 services to work in an IPv6-only environment. It's nice to only have one stack to administrate, and IPv6 is generally more flexible, but you often need to fall back to IPv4.

NAT64 is more and more used instead of CGNAT (well, it's still CGNAT to an extent), but I don't really see one being advantageous over the other. Only that there are only IPv6 semantics when using NAT64, so stuff like roaming, privacy extensions, etc. works, and you don't have to rely on dual-stack.

I think the big advantage to NAT64 is identifying the pain points (incompatible equipment, applications, etc) in an IPv6-only world. And it really is a clear transition path to IPv6.

[xmichael0]

Thank you for your comprehensive and thoughtful answer. I agree with everything you said, except for the idea that we are transitioning, we will always live in a hybrid ipv4 ipv6 world (;

[MayeulC]

Ah, but those who live behind NAT64 are already living in an IPv6-only world ;)

Do you really think there will never be IPv6-exclusive services? I personally think it's bound to happen, if only some private websites here and there. Maybe some country will make a bit push? At this point, not having IPv6 connectivity starts being a liability.

Going forward, whether everyone adopts IPv6 or not doesn't really matter I think. Legacy equipment will carry on under IPv4, even if it is just NATed IPv6. Servers, intranets and VPN can keep on using v4 if they prefer, but servers will need to be dual-stack if they need to contact IPv6 hosts (databases, APIs, websites). NAT64 (with a dedicated IPv4) is a clean way to handle dual-stack, I wonder if it will be, or is already available in datacenters?

Thinking more about it, these semi-public API endpoints is where the transition might happen first: some services already leverage IPv6, like smart power meters. If both endpoints are controlled by the same entity, it's quite easy to make them IPv6-only, especially if public access is possible, but not a priority.

Keep in mind those are my opinions, I am not a network professional!

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I wonder how much longer it will take for publicly available IPv6-only services to appear? 10 years? 20 years? Once they start appearing, how long will most ISPs take to deploy IPv6? 5 years? What if, say Belgium mandates its ISP to provide IPv6 connectivity? Would that boost adoption in the Netherlands?

In the end, it's easy to contact IPv4 hosts if you only have IPv6, but the opposite isn't true, because only one can encapsulate the other.

If IPv6+NAT64 starts being a viable and widely adopted option, will we have a surplus of IPv4 addresses? Will websites start to block IPv4 due to spam issues?

If enough people like me are eager to transition, we will transition somewhat... due to network effects :)

[betterunix2]

I doubt that we will always live in a hybrid world. IPv4 address space exhaustion is a growing problem and NAT is at best a partial solution. As more ISPs resort to things like NAT64 and 464XLAT the shortcomings of NAT (of whatever form) will become a larger problem and developers will start writing IPv6-only applications. After enough time IPv4 service will become optional, and shortly thereafter irrelevant.