Hello!
Our old anti-fraud system requires ipv4 only, but we don’t want to disable ipv6 at all.
Pseudo-ipv4 is undesirable, because we need real ip.
How to make CF use ipv4 if client supports it ? How to make CF use ipv6 ONLY if client doesn’t have ipv4.
Thanks!
Thats not something up to Cloudflare. You need to configure your client accordingly.
Client = Surfer, Web visitor. I can’t configure customer’s computers. I need make CF don’t use ipv6 if surfer have ipv4.
I understood that, but that is still something you have no control over. All you can do is disable IPv6 altogether.
Ok. Sad 
Thank you for answer.
The way DNS works under the covers (especially on mobile devices) is covered by the Happy Eyeballs RFC. Simple version… mobile devices query for an IPv6 address first and if no response in 20ms will issue a second query for IPv4 and only use the IPv4 response if it comes back first.
So short I’d intentionally making their IPv6 responses slooooow there isn’t really anything a DNS operator could do to influence the behavior.
— OG
