ACL to determine if basic auth is used


Hi all. I hope someone can help me. I need an ACL command to determine if basic authentication is being sent to root this to the correct backend.
A little background. I have a new server that uses basic auth. But it will be a staged switchover and I need to move one client at a time. It would help if I can rout all the request to the old server without authentication.
Please help


HTTP auth has to be solicited by the server, therefor I don’t see how what you have in mind can be done.


Thank you for the info.