Don't be tortured by Cloudflare! 1016, 521, 522, 523 errors are so much worse!

When the site is accessed Cloudflare After that, one of the most common problems is access reporting errors. Many webmasters are confused when they first encounter "Error 1016" or "521" "522" "523 " are confused: these numbers look similar, but have completely different meanings and solutions. This article will deeply analyze the difference between these four types of errors, causes and the most effective troubleshooting ideas to help you quickly locate the problem and restore normal access.

I. Overview of the core differences between the four errors

error code	misstatement	root cause	typical scenario
1016	Origin DNS Error	Cloudflare can't resolve the source domain	Source station records are missing or pointing in the wrong direction
521	Web Server Down	Connection denied by source or blocked by firewall	Source station not running, port blocked
522	Connection Timed Out	Cloudflare connection timeout with source	Slow server response or network congestion
523	Origin Is Unreachable	Cloudflare cannot access the source IP	Invalid DNS pointers or IP changes

As you can see, although they all belong to the "source connection class error", but essentially divided into two categories:

• DNS level errors (1016, 523): Cloudflare cannot find or access the source site.
• Network level errors (521, 522)::Cloudflare The source station was located but could not communicate properly.

Error 1016: DNS resolution errors are most common

misdescription::
When Error 1016 Origin DNS Error appears, it means that Cloudflare It is not possible to resolve the source domain name at the proxy level, i.e. it has no idea where the source IP address is.

Common Causes:

• Domain A record or CNAME record is deleted or misconfigured.
• The source station points to an invalid hostname (e.g. CNAME loop).
• A third-party CDN or subdomain was used but did not resolve correctly in Cloudflare.

Diagnosis and Repair:

• Check the Cloudflare panel for complete DNS records (A or CNAME).
• utilization nslookup yourdomain.com maybe dig yourdomain.com Verify the parsing results.
• If you use CNAME, make sure you end up with a valid IP address.
• Avoid nesting another domain that is being proxied by Cloudflare in the CNAME.

Summary:Error 1016 is purely a parsing issue, and the solution is almost always at the DNS level.

III. Error 521: Connection refused by source station

Misdescription:
Cloudflare The server can be found, but the connection request is denied.

Common Causes:

• The source Web service (e.g., Nginx, Apache) has stopped running.
• Firewalls or security plugins (e.g. fail2ban, CSF) mistakenly block Cloudflare IPs.
• The server allows only local access or specific IP whitelisting.

Diagnosis and Repair:

• Log in to the server and verify that the Web service starts normally.
• Check firewall rules to make sure they are not blocked Cloudflare The official IP segment of the
• Look for "connection refused" type messages in the Nginx or Apache error logs.
• utilization curl -v http://yourdomain.com Test that the local connection to the source station is working.

Summary:521 is more of a "source not responding", focusing on server status and security policy.

IV. Error 522: Connection Timeout

Misdescription:
Cloudflare The source station was successfully found, but the TCP handshake could not be completed within the preset time.

Common Causes:

• The server at the source site is overloaded and responds too slowly.
• Network congestion or intermediate link delays.
• The port is misconfigured (e.g., only 8080 is enabled instead of 80/443).

Diagnosis and Repair:

• utilization ping (computing) maybe traceroute Check network connectivity.
• View server CPU and memory usage to avoid resource overload.
• Check if the wrong port or protocol is enabled in the Cloudflare panel.
• If it is a high-traffic site, it can be turned on Cloudflare Argo Smart Routing" feature to optimize routing.

Summary:522 is essentially a network performance problem, and the key to solving it is to optimize the response speed and network quality of the source station.

V. Error 523: source station unreachable

Misdescription:
Cloudflare Unable to access the source IP, similar to "DNS pointer exists but cannot connect".

Common Causes:

• The source IP has been changed but the DNS has not been synchronized.
• The server is down or the IP is blocked by a firewall.
• An IPv6 address conflict or incorrect resolution caused the connection to fail.

Diagnosis and Repair:

• Update the latest IP address in Cloudflare.
• utilization ping (computing) respond in singing curl command to access the source station directly for verification.
• If it is a multi-NIC server, make sure the external IP is configured correctly.

Summary:The focus of the 523 is on IP-layer access, usually with breakpoints at the DNS or network layer.

VI. Ideas for a comprehensive ranking of the four errors

1. Check the DNS level first:
   Use the Cloudflare panel with the dig tool to confirm that the records are correct.
2. Check the server status again:
   Ensure that web services are running, ports are open, and firewalls allow it.
3. Finally the link quality is measured:
   utilization ping (computing),traceroute,curl Test actual connectivity.

If you are using shared hosting or cloud servers, you can also contact your service provider to confirm IP changes, port policies, or blocking rules.

VII. Summarize: understanding the error code is the key to efficient troubleshooting

error code	Type of problem	direction of the solution
1016	DNS not resolving	Check A/CNAME records
521	The source station refuses to connect.	Check server status, firewalls
522	network timeout	Optimize response, check ports
523	IP unreachable	Updating IPs, repairing network links

Understanding the triggering conditions for each error allows you to quickly pinpoint the problem.Cloudflare The error codes are numerous, but as long as you follow the DNS → Server → Network of three layers of troubleshooting logic, almost all of which can be resolved in a matter of minutes.

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