Troubleshooting Cloudflare connections

If you experience connection-related issues with your web site when Cloudflare is enabled, this article provides information you can use to troubleshoot and help determine the cause.

Cloudflare error pages

One of the most common (and visible) indications of a problem is when your site displays a Cloudflare error page instead of your own content. These error pages can provide valuable information about why your site is not loading correctly.

There are several scenarios where Cloudflare displays an error page:

• 520 Web server is returning an unknown error: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200171936-Error-520.
• 521 Web server is down: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200171916-Error-521.
• Error 522 - Connection timed out: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200171906-Error-522.
• 523 Origin is unreachable: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200171946-Error-523.
• 524 A timeout occurred: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200171926-Error-524.
• 525 SSL handshake failed: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200278659-Error-525.
• 526 Invalid SSL certificate: For information about this error message, please visit https://support.cloudflare.com/hc/en-us/articles/200721975-Error-526.

Site DNS settings

For Cloudflare to work, your domain's nameserver settings must be configured to route traffic through their network.

To verify that your site is configured at the DNS level to use the Cloudflare network, follow these steps:

1. Log in to your account using SSH.
2. At the command prompt, type the following command. Replace example.com with your own domain name:

   dig www.example.com

3. In the dig command output, look under AUTHORITY SECTION:
   

   • If a hostname with cloudflare.com is included in the response, go to step 4. (For example, dns.cloudflare.com or ns.cloudflare.com)
   • If cloudflare.com is not included in the response, your domain's DNS is not configured to use Cloudflare.

4. On your local computer, use dig or nslookup to query www.example.com, where example.com represents your domain name.
   

   For information about how to use dig or nslookup on your own computer, please see this article.
   • If a hostname with cloudflare.com is included in the response, then your domain's DNS settings are working along the entire connection path from your local computer to Cloudflare to the server.
   • If cloudflare.com is not included in the response, the problem is not with Cloudflare. Your local computer or network may have a configuration issue preventing access to the Cloudflare network or your site.

More Information

For more information about Cloudflare, please visit https://www.cloudflare.com.