Error code 521

@waseemsannib

Error code 521 indicates that Cloudflare is unable to establish a connection to your origin web server. This can occur for several reasons, particularly after changing your DNS settings to connect your website to Cloudflare. Here’s a breakdown of potential causes and solutions: Possible Causes of Error Code 521

• Web Server Issues: Your origin server might be down or not responding. Ensure that your web server is running properly and check its error logs for any issues.
• Firewall or Security Settings: Your server’s firewall may be blocking Cloudflare’s IP addresses. Make sure that your firewall settings allow connections from Cloudflare IPs and are not set to block or rate limit them.
• Incorrect DNS Configuration: If your DNS settings are not correctly configured, Cloudflare may not be able to reach your server. Double-check that the nameservers and DNS records are set up correctly in your hosting provider’s control panel.
• SSL Configuration: If you are using HTTPS, ensure that your server is configured to accept connections on port 443. If necessary, consider switching to “Flexible” SSL in Cloudflare’s SSL/TLS settings, which can help if your origin server does not support SSL.

Steps to Resolve the Issue

1. Check Server Status: Verify that your web server is operational. You can do this by accessing it directly via its IP address.
2. Review Firewall Settings: Ensure that your firewall is not blocking Cloudflare’s IP addresses. You may need to whitelist these IPs.
3. DNS Propagation: As you mentioned, DNS changes can take up to 24 hours to propagate fully. If you have just made the changes, it may be worth waiting to see if the issue resolves itself.
4. Contact Hosting Provider: If you are unable to diagnose the problem, reach out to your hosting provider for assistance. They can check if there are any issues on their end that might be causing the connection failure.
5. Test with Development Mode: If you have access to Cloudflare, try enabling Development Mode temporarily. This can sometimes bypass caching and allow you to see if the site is accessible without Cloudflare’s interference.

Conclusion

In summary, the error code 521 is likely due to connectivity issues between Cloudflare and your origin server, which could stem from server downtime, firewall settings, or DNS misconfigurations. It is advisable to check your server’s status, review your firewall settings, and possibly wait for DNS propagation. If the issue persists, contacting your hosting provider for further assistance is recommended.

Citations:
[1] https://wordpress.org/support/topic/error-code-521/
[2] https://community.cloudflare.com/t/error-code-521/418286
[3] https://community.cloudflare.com/t/community-tip-fixing-error-521-web-server-is-down/42461
[4] https://community.cloudflare.com/t/getting-http-521-randomly-on-my-website-with-the-proxy-option/627172