Server down warning periodical - related to server firewall - CF Ip ranges added

[phillip4]

What is the name of the domain?

website domain

What is the error number?

521

What is the error message?

web server is down

What is the issue you’re encountering

Site did have proxied dns through you but something was interfering with our firewall on our server. we get errors that says server down and host error (but its not) …it comes and goes…I have added Cloudflare listed IP address ranges to rule allowing them full access but we still periodically get this issue. when the firewall is turned off the issue goes away but cannot understand why if the IP ranges are allowed. can anyone confirm why this would be?

What steps have you taken to resolve the issue?

I have added the full IP range up to date to firewall exemptions

What are the steps to reproduce the issue?

Using plesk firewall enabled, add exemption for Cloudflare IP ranges.

Screenshot of the error

[Laudian]

It sounds like you are using fail2ban or a similar software that automatically bans IP addresses when certain conditions are met.

As the problem disappears when you disable the firewall, you’d need to find out what software is causing your firewall to block Cloudflare IPs.