The domain that you will set in the Custom Host Header will instruct the Origin Shield server to replace the request host header value (e.g. domain) for every request proxied to the origin.
In other words, when the Origin Shield server contacts the origin’s IP address, it will use the new value in the request host header instead of the original one.
To set up Custom Header, navigate to ‘Multi CDN’ > ‘General Settings’ > ‘Custom Host Header’ box.
On the Custom Header box, click the ‘Settings’ (gear) icon, then write the Custom Host Header domain on the field.
Finally, click the ‘Save’ button.
Make sure the request host header value can be recognized by the origin server, else you may experience proxy connection errors such origin server not returning a response, or returning a response to redirect the request to a different domain. Also, make sure that the set domain will not cause redirect loops.