user00265

I would love to challenge that -- fully working IPv6 setup here through Hurricane Electric. All device that are dual-stack capable on the network work... except for my Unraid NAS. I've tried everything else on this thread and nothing got the connection to work until IPv6 was disabled. As mentioned by @CorruptComputer, turning off IPv6 on the NIC gets the connection re-established. Turning it back on causes the connection to not work. This is the first device I have found with any issues in my network, so I don't believe this to be "a general networking issue" and perhaps more of the underlying cause in the specific setup. Is the cloud service endpoint IPv6 capable? Is it advertising an IPv6 address? Is it responding normally like the IPv4 counterpart? Is the code able to handle either address family? Anything hard-coded that may expect IPv4 but will not handle an IPv6 address? A simplistic example is the Transmission portcheck service. For a while it was working fine with IPv4 queries, but any dual-stack hosts that used the (published in DNS) IPv6 address would get a "400 Bad Request" error. I believe this was fixed this year, even.