Troubleshooting Tip: How to check and fix 'Request entity too large' error on a large file upload POST request to Apache Server when the proxy is behind FortiWeb

Description

This article describes how to check and fix an error on a large file upload POST request to Apache Server when the proxy is behind FortiWeb.

Scope

FortiWeb.

Solution

1. There are cases where the back-end Real Server is using an Apache Web Server and users encounter errors when performing large file upload to the website hosted in the Apache Web Server.

Example error:

2. The error page would be returned from the Apache Web Server instead of the FortiWeb. The traffic log in FortiWeb is showing that the Apache Web Server is returning the return code '413'.

3. Check the Apache Web Server log. It will show an error related to SSL buffer and SSL renegotiation.

4. Take note that these errors are not the blocking from FortiWeb but limitation errors from the Apache Web Server configuration. To fix the error, increase the SSL Renegotiation buffer size by adding the config line below in the Apache virtual host config file, then save the changes and reload/restart the Apache Web Server service.

SSLRenegBufferSize <bytes variable> (default value: 131072)