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Error 523

Error 523: origin is unreachable

This error occurs when Cloudflare cannot contact your origin web server.

Common causes

This typically occurs when a network device between Cloudflare and the origin web server does not have a route to the origin's IP address.

In AWS environments, a common cause is an overly broad route such as 172.0.0.0/8 in a VPC route table. Cloudflare uses public IP ranges in 172.64.0.0/13, and a broad route can accidentally capture traffic intended for Cloudflare.

Resolution

Contact your hosting provider and share the necessary error details to exclude the following common causes at your origin web server:

  • Confirm the correct origin IP address is listed for A or AAAA records within your Cloudflare DNS app.
  • Troubleshoot Internet routing issues between your origin and Cloudflare, or with the origin itself.
  • In AWS, review VPC route tables and make sure you are not sending 172.64.0.0/13 toward a private destination. If required, add a more specific route for 172.64.0.0/13 to your Internet Gateway.

If none of the above leads to a resolution, request the following information from your hosting provider or site administrator:

  • An MTR or traceroute from your origin web server to a Cloudflare IP address ↗ that most commonly connected to your origin web server before the issue occurred. Identify a connecting Cloudflare IP from the logs of the origin web server.