It is a common setting to configure CDN back to the intranet server to improve the security and performance of the website. This configuration ensures that when external users access content, the request will first pass through the CDN server, and then go back to the source to obtain the content through the intranet server. The following are the general steps to implement CDN back-to-origin to the intranet server:

　　Intranet server preparation:

　　First, make sure your intranet server is ready and can properly provide the required website content. Make sure the server is properly configured and accessible from the outside.

　　CDN service provider settings:

　　Log in to the management backend of your CDN service provider and find the option for back-to-origin settings.

　　Set the return-to-source address:

　　In the management background of the CDN service provider, you need to set the return-to-source address, which is the address of the intranet server. Usually this involves filling in the IP address and port number of the intranet server.

　　Port Mapping:

　　If the port of the intranet server is not 80 (HTTP) or 443 (HTTPS), you may need to perform port mapping to correctly map the CDN server's request to the port of the intranet server.

　　security strategy:

　　To ensure security, you may need to set an access control policy to only allow the CDN server to access the intranet server to prevent other unauthorized access.

　　Testing and debugging:

　　After completing the setup, conduct a test to ensure that the CDN can successfully return to the intranet server. You can test whether everything is normal by visiting the CDN-accelerated website.

　　Monitoring and optimization:

　　After the setup is completed, regularly monitor the back-to-origin status of the CDN to ensure the stability and performance of the intranet server. Make adjustments and optimizations as needed.

　　Please note that the setup interface and steps of each CDN service provider may be different, and the specific steps may vary depending on the service provider. Before setting up, it is recommended to check the documentation of the CDN service provider you are using or contact its support team to obtain accurate operation guidance. Also, make sure to back up important configuration files and settings when making any changes to prevent the unexpected.