Plesk for Linux kb: technical
- Plesk Linux
- Plesk for Linux
- When visiting the website, it fails to load with error 521:
The error occurs because the origin web server refused the connection from CloudFlare.
CloudFlare IP addresses were blocked by
nginx configuration because of outdated contents of
- Connect to the server via SSH;
/etc/nginx/conf.d/cloudflare.confand make sure that it is up to date and contains all IP addresses found here: https://www.cloudflare.com/ips;
- Additionally, make sure that CloudFlare IPs are not blocking by firewall or Fail2ban;
in case 521 error will be resolved by one of solution below - separate article needed
- Make sure your provider doesn't rate limiting or blocking IP requests from the CloudFlare IPs and ask them to whitelist the IP addresses found here: https://www.cloudflare.com/ips;
- Make sure that you're operating off of the most recent versions of Bad Behavior or
mod_security. You want to ensure that mod_security's core rules aren't blocking CloudFlare requests;
- If you are running custom Apache modules, such as
mod_reqtimeout, disable and unload the modules. These modules will block any time an IP that connects more than 22 times. Since all connections are now coming from a CloudFlare IP, you will definitely hit the limit causing the error page. As soon as you unload the module, the issue will disappear.
- If the issue persists, please visit CloudFlare article regarding this issue.