| A big part of it is how much actually needs to change, and work properly, before you can actually rely on IPv6 the way you can on IPv4. I recall reading about Facebook's internal IPv6 migration for their data centers and the problems they ran into. The two that stuck out the most to me and which I still remember details for are: 1. The PHP function developers used to convert an IPv4 address into an integer to store into a database or something. It didn't work in IPv6, meaning the code broke badly when it was considering an IPv6 host. They kept asking developers to stop using it, but new code kept getting added which used it. Eventually the decision was made that 'we've warned you enough, so from now on we're just going to go ahead and let your code break'. 2. Their networking hardware wasn't extensively tested for an IPv6 single-stack deployment. Turns out that when presented with a BGP advertisement that contained only IPv6 routes and no IPv4 routes, their switches would immediately crash. How did they discover this? By sending out a BGP advertisement that contained only IPv6 routes and no IPv4 routes, crashing every rack switch in the data center. There's no reason why this should happen; it's not a violation of the BGP spec or anything, it's just a bug for a case that no one tested on the vendor's end because none of their customers tried to do that. So it's not that IPv6 sucks; it's actually pretty great in a lot of ways. The problem is that everything else sucks; people don't bother to support things, they don't consider it in their code, they don't test for it, they don't bother to roll out support because no one else has done so either so why bother, and so on. In the end, IPv6 is 'avoided' because of the problems that Facebook ran into, or that OP ran into, and is 'resisted' because it's extra work that they could put into doing other things with their limited time and engineering work. To be clear, dual-stack deployments work great; my ISP recently did a trial of a dual-stack deployment which I was lucky enough to participate in, and it was almost completely transparent. My Unifi gateway picked up the address and handed addresses out to clients internally, clients used IPv6 where appropriate and fell back to IPv4 when necessary, and everything worked completely transparently. TL;DR IPv6 isn't the problem, the industry is the problem. |