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Cloudflare Error 521 Troubleshooting Guide
phoenixnap.com/kb/error-521Yapay zekadan makale özeti
- Understanding the Error
- Error 521 occurs when Cloudflare cannot connect to the origin server
- Error happens when origin server is offline or has Apache/Nginx issues
- Cloudflare acts as intermediary between browser and origin server
- Common Causes
- Origin server being offline or experiencing configuration problems
- Blocked Cloudflare IP addresses in server-side security
- Incorrect server configuration for CDN usage
- Slowloris modules causing dropped packets
- Troubleshooting Steps
- Check origin server's HTTP status using cURL or online tools
- Whitelist Cloudflare IPs in .htaccess or firewall rules
- Install valid SSL certificate through Cloudflare Origin Server
- Review mod_security module settings
- Disable mod_antiloris and mod_reqtimeout
- Check Railgun configuration
- Contact Cloudflare Support if issues persist