---
title: Error 523
description: Troubleshoot HTTP 523 error responses.
image: https://developers.cloudflare.com/core-services-preview.png
---

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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](https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/#required-error-details-for-hosting-provider) 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](https://developers.cloudflare.com/support/troubleshooting/general-troubleshooting/gathering-information-for-troubleshooting-sites/#perform-a-traceroute) from your origin web server to a [Cloudflare IP address ↗](http://www.cloudflare.com/ips) 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.

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