I’ll paste a comment that illustrates it better than I could
Imagine this scenario - you’re a corporate with 1000 sites and maybe 5000 networking devices. You have a rolling replacement program for those devices as they become end of life, and as that progresses you reach a point where all of them can work with IPv6. So you switch off IPv4 and work only with IPv6.
Then your corporate acquires another entity, say consisting of 100 sites with 500 devices. All of those devices need checking that they can work on IPv6 and a significant number need replacing at maybe an average of £5000 per device. With IPv4 you can still integrate the legacy kit into your estate without swapping any of it out, with IPv6 only you can’t.
For an end user, a small startup, or similar sure go ahead and use IPv6, but there are significant obstacles for larger estates, which is one reason IPv4 isn’t going anywhere soon.
Why would anyone switch off IPv4? That makes no sense and isn’t commonly done. You run dual stack in most cases – NAT v4 and straight v6. A lot of folks are using v6 on mobile phones without even realizing it because telcos ran the numbers years ago and realized it was cheaper to push v6 at the end user layer than run NAT and/or try to find v4 addresses on the transfer market. There’s been no unallocated pool of v4 space for almost a decade.
Hey guys, I deployed our servers on 10.0.0.0/14 and didnt’ bother with ipv6. Oh no! The company that we just acquired also deployed their servers on 10.0.0.0/14, so all of your assumption in your dumb-ass contrived scenario are invalidated.
ipv6 adoption only matters for public reach. Right now if you want a website accessible by 75% of the world, it has to be an ipv4 endpoint. Though that is changing. Here is a blog post by someone from akamai in 2018 talking about the rapid adoption of ipv6.
https://www.akamai.com/blog/performance/six-years-since-world-ipv6-launch
Basically if you aren’t deploying a service as native ipv6, you’ve already fucked up.
I’ll paste a comment that illustrates it better than I could
Why would anyone switch off IPv4? That makes no sense and isn’t commonly done. You run dual stack in most cases – NAT v4 and straight v6. A lot of folks are using v6 on mobile phones without even realizing it because telcos ran the numbers years ago and realized it was cheaper to push v6 at the end user layer than run NAT and/or try to find v4 addresses on the transfer market. There’s been no unallocated pool of v4 space for almost a decade.
Yes that’s the odd part. Most people are using v6 daily without even realizing it.
Hey guys, I deployed our servers on 10.0.0.0/14 and didnt’ bother with ipv6. Oh no! The company that we just acquired also deployed their servers on 10.0.0.0/14, so all of your assumption in your dumb-ass contrived scenario are invalidated.
ipv6 adoption only matters for public reach. Right now if you want a website accessible by 75% of the world, it has to be an ipv4 endpoint. Though that is changing. Here is a blog post by someone from akamai in 2018 talking about the rapid adoption of ipv6. https://www.akamai.com/blog/performance/six-years-since-world-ipv6-launch
Basically if you aren’t deploying a service as native ipv6, you’ve already fucked up.
Most competent IT departments would just set up bidirectional NAT.
https://www.juniper.net/documentation/us/en/software/session-smart-router/docs/config_static_nat/
was that comment written in 1996