Cloudflare Cloudflare IPv6 Compatibility & Pseudo IPv4

If you are using Cloudflare in front of your server, then Cloudflare will resolve your domain over both IPv4 and IPv6 Cloudflare IP addresses. But if your Centmin Mod Nginx origin doesn't support IPv6 or has IPv6 disabled, you may need to enable Pseudo IPv4 for compatibility in Cloudflare > Network tab and setting it to overwrite headers.

Example for this forum behind Cloudflare doing DNS A and AAAA lookups returning Cloudflare's IPv4 A record and Cloudflare's IPv6 AAAA record.

Code (Text):

dig +short A community.centminmod.com 
104.20.230.85
104.20.231.85

Code (Text):

dig +short AAAA community.centminmod.com
2606:4700:10::6814:e755
2606:4700:10::6814:e655

verify if your server supports IPv6 using ping6 command on your Centmin Mod server

Code (Text):

ping6 -c4 community.centminmod.com

if IPv6 supported output for ping6

Code (Text):

ping6 -c4 community.centminmod.com
PING community.centminmod.com(2606:4700:10::6814:e755 (2606:4700:10::6814:e755)) 56 data bytes
64 bytes from 2606:4700:10::6814:e755 (2606:4700:10::6814:e755): icmp_seq=1 ttl=61 time=0.398 ms
64 bytes from 2606:4700:10::6814:e755 (2606:4700:10::6814:e755): icmp_seq=2 ttl=61 time=0.360 ms
64 bytes from 2606:4700:10::6814:e755 (2606:4700:10::6814:e755): icmp_seq=3 ttl=61 time=0.531 ms
64 bytes from 2606:4700:10::6814:e755 (2606:4700:10::6814:e755): icmp_seq=4 ttl=61 time=0.328 ms

--- community.centminmod.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3002ms
rtt min/avg/max/mdev = 0.328/0.404/0.531/0.078 ms

if IPv6 not supported or broken on server for ping6 output

Code (Text):

ping6 -c4 community.centminmod.com
connect: Network is unreachable

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As @Rake-GH reminded me, Cloudflare's Pseudo IPv4 feature is now default enabled so you no longer need to turn it on anymore But double check your settings to make sure.