Cloudflare seem to prefer ipv4...
I don't know if this is accurate, but I found today that Cloudflare prefers ipv4, if used as round robin system. I installed some servers, some of them ipv4 and some of them ipv6 only and tried to setup a round-robin system for a single web page. I want availability to the servers via a single normal domain name, accessible to the users that only have access to ipv4 in their home's isp.
I use for that the ipv6 gateway cloudflare offers for html access (port 80).
The odd thing is that when I put it to work, I can have access only to the servers that has ipv4 on the A input at cloudflare dns. That does not mean that others do not resolve via Cloudflare. They do, but only if I delete A entries (ipv4) and let only the servers that has ipv6.
I noticed that because the html in each server is differently numbered to identify witch server I am accessing.
So, it seem that if you enter a lot of servers in a single domain name (both A ipv4 and AAAA ipv6 entries), cloudflare will resolve only those in ipv4. If you have in this roundrobin setup only ipv6 servers, then, they are shone normally!
has anyone noticed that or have any knowledge about it?