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Cloudflare Error 521: Proven Troubleshooting Tips » Voxfor

How to Fix CLOUDFLARE ERROR 521. Also shown as “web server is down”. It indicates that the website is experiencing a server-side problem. It is a common error that affects Cloudflare-enabled websites.This actually happens when the web server refuses the connection from cloudflare and Cloudflare is unable to make a TCP connection to the origin web server. It means that the server is not accepting requests from Cloudflare’s network

some common reasons for encountering a Cloudflare Error 521 are:

  • The origin web server may be down, unreachable, or experiencing connectivity issues. This could be due to server maintenance, network outages, or other technical issues.
  • Firewall rules or security software configured on the origin server may be blocking incoming connections from Cloudflare’s IP addresses. This could be intentional or due to misconfigurations.
  • The origin server may be overloaded or experiencing high traffic, causing it to become unresponsive to incoming requests from Cloudflare.
  • Network routing problems between Cloudflare’s data centers and the origin server can prevent successful connections. This could be due to misconfigurations, DNS issues, or ISP-related problems.
  • If the origin server requires SSL/TLS connections but has an invalid, expired, or misconfigured certificate, Cloudflare may fail to establish a secure connection, resulting in Error 521.
  • Incorrect server configurations, such as incorrect IP address or port configurations, can prevent Cloudflare from establishing a connection with the origin server.

To troubleshoot and resolve a Cloudflare Error 521, you can try the following steps:

  • Check Origin Server Status: Verify that the origin web server is up and running, and that there are no ongoing maintenance activities or outages.
  • Review Firewall and Security Settings: Ensure that firewall rules or security software on the origin server are not blocking incoming connections from Cloudflare’s IP addresses. Whitelist Cloudflare IP addresses if necessary.
  • Optimize Server Performance: If the origin server is overloaded, consider optimizing its performance by reducing server load, optimizing configurations, or adding additional resources to handle incoming traffic.
  • Check SSL/TLS Configuration: Ensure that the SSL/TLS configuration on the origin server is correct and that the server has a valid SSL/TLS certificate installed.
  • Review Network Configurations: Check for any network routing issues, DNS misconfigurations, or ISP-related problems that may be preventing successful connections between Cloudflare and the origin server.

If the issue persists after troubleshooting these steps, you may need to contact your hosting provider, network administrator, or Cloudflare support for further assistance in diagnosing and resolving the Error 521.

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