Novadays isp assign to servers not only a static ipv4 address, but a static ipv6 too. The trend for the future is to point in ipv6 directon. On mirrored server setup, ispconfig has the ipv4 mapping feature. Should be a good thing to do the same on ipv6 (the ipv6 rewrite future is kind of useless because assigns random ip suffix). On load balancer or high availability server setup or even with dns mirroring this is mandatory, or it "just don't work". Thank you all for this great piece of software.