If you have a SSRS Customized Report (.RDL). and a web part with association on one of the report. When you try visit the page you are prompted for credential.
My Data Source Properties are as per below
Use this user and Password
user name: domain\myadminuser
Selected: use as windows authentication
Cause & Solution:
In the cases I have seen, the problem is due to Kerberos authentication. Kerberos is an authentication protocol that allows clients that create authentication tokens to associate a specific destination to that token. In the failure case there is a mismatch between the destination specified in the token and the report server process configuration. Due to this mismatch, the underlying Kerberos authentication scheme supported by Windows prevents report server from authenticating the user
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