The IIS web server has been set to allow anonymous access, but the client still requires the user name and password to be entered.

The IIS server has been set to allow anonymous access, but the browser client still requires the user name and password to be entered. Access via localhost on the server is not required, and access via IP address is required.
Solution:
Change the anonymous IIS access user to the system administrator.
Other solutions:
The above method is temporary, and the security is poor. the cause of this error may be that the IIS user permission configuration is lost or that the user is disabled. or the Temporary Folder permission for Asp.net is insufficient. after all these possible errors are excluded, the problem should be solved.
Multiple servers may also be caused by network settings, such as improper DNS configuration.