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Ágoston Horváth
There are still a few topics you did not mention. - load balancing/virtual IP. In ipv6, two hosts on the same subnet can not have the same IP; if they do, neighbor discovery would disable it on all but one. You need a whole different approach to low-cost/masterless load balancing. - NAT hiding the IPs behind does have a valuable boost on privacy. Indeed, you can still distinguish unique clients via other means, but it does remove the most glaring way to do so. - Re-assigning IPs all the time makes firewall more complex, as anything can change. - Generally, I consider the semi-intelligent nature of the IPv6 network a disadvantage. It makes configuration more complex compared to v4, with a steep learning curve, and all for something that is prone to change. Ipv4 being static did have an advantage of better control and overview by sysadmins. E.g. even a simple packet monitoring is now disrupted by ipv6 traffic and reconfiguration. Overall I think that injecting _a lot_ more than just extended address space into ipv6 was a mistake, that has an effect is very slow transition that is observed right now. Effectively, people would hold out migrating to ipv6 unless absolutely necessary. That alone is a feedback that it is not considered a distant advantage.