Dns doesn't always resolve correctly

Website, Application, Performance DNS & Network
1

I’m hoping I explain this correctly.

I have a domain, let’s call it mydomain com and it has an IP address of 21 21 21 21 (not real).
I have a bunch of cnames that point to mydomain com and its IP. For instance, nginx mydomain com.
21 21 21 21 goes to a fortinet firewall that forwards all port 80 and 443 traffic to an nginx proxy manager server inside the lan…

I have the domain at cloudflare proxied… so if I ping mydomain com, I get the 104 21 49 109 IP address. Which is what I expect. I do NOT have the CNAME proxied (I can’t get the fortinet to route correctly if the cname is proxied and it sends back the cloudflare IP), and when I ping nginx mydomain com, it resolves and pings at 21 21 21 21. This is my default WORKING setup.

This has been working months. However, every once and a while now, nginx mydomain com will quit responding from WAN. If I connect to it inside the LAN on it’s local address, it is working fine.

The only way I can seem to get it to work again is if I log into the cloudflare DNS manager, turn off PROXY on my main domain, wait 10 minutes, turn PROXY back on, wait another 10 minutes and then my site resolves and responds from the WAN again.

I appears random, but the solution has worked every time (so far); however, it’s a huge pain in the…well you know what.

Any ideas? I wondered if it has something to do with caching. But that is honestly a guess.

Any help or suggestions would be greatly appreciated and sorry for all the messed up ip and domain spacing.

Thanks,
Tim

4

Anyone have an idea?

5

Your description is a bit strange so hard to work out what could be happening, can you share the domain name?

When you say “nginx mydomain com will quit responding from WAN”, is that via the Cloudflare proxy or if you use the origin’s direct IP address? If the latter, then it must be an issue on your origin.

Are you running anything like denyhosts or fail2ban that may be blocking Cloudflare proxy IPs at the origin and clearing later or when the IP changes?

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