My origin server is reachable only via an IPv6 (my Internet Provider has only shared IPv4 addresses, making my resources unreachable over an IPv4 address).
I have configured only an AAAA record in my DNS zone (with no A type record).
Theoretically CloudFlare should be able to reach my origin server by name (from both ipv4 only and dual stack ipv4/ipv6 networks), as I can when using the IPv6 address from different networks over the Internet.
But via CloudFlare there is always a “Web server is down: 521” error.
There is no firewall issue.
A network sniff shows there is no activity between CloudFlare and my origin server when reaching by name.
Ray ID: 5edcef4b7be5acfa
2020-11-06 06:59:57 UTC