When troubleshooting Kerberos authentication issues related to SPNs in Tableau Server, what common problem should be investigated first?

A Service Principal Name (SPN) is a unique identifier for a service instance. In a Kerberos environment, clients use the SPN to request a service ticket from the Key Distribution Center (KDC) to authenticate to Tableau Server. If the SPN is not correctly registered in Active Directory for the Tableau Server "Run As User" account, the KDC cannot locate the service and will fail to issue a ticket, causing authentication to fail. This is one of the most common and fundamental configuration errors in a Kerberos setup, making it the primary point of investigation when SPN-related issues are suspected.

A. Ticket expiration is a general Kerberos timing issue, not a specific problem with the SPN's registration or identity.

C. A firewall blockage is a network-level problem that would prevent any Kerberos communication, not an issue specific to the SPN configuration itself.

D. This is a client-side configuration requirement. Server-side issues, particularly SPN misconfiguration which affects all users, are typically investigated first.

1. Tableau Server Documentation: In the "Troubleshoot Kerberos" section

the first verification step listed after checking the keytab file is to verify the SPN. It states

"Verify the SPN is set on the Run As User account... If the SPN is not set correctly... Kerberos authentication will fail."

Source: Tableau Help

"Troubleshoot Kerberos"

Section: "Kerberos configuration checklist".

2. Microsoft Documentation: Microsoft's documentation on Kerberos explains that a missing or incorrect SPN is a primary cause of authentication failure. The KDC uses the SPN to find the service account to encrypt the service ticket. If the SPN is wrong

the process fails at this critical step.

Source: Microsoft Docs

"Service Principal Names"

Section: "How SPNs Work".

3. MIT Kerberos Documentation: The official MIT documentation outlines the Kerberos protocol

where the client's request to the KDC for a service ticket (TGS-REQ) includes the SPN of the target service. An incorrect SPN prevents the KDC from finding the service's key to create the ticket.

Source: MIT Kerberos Documentation

"Kerberos V5 System Administrator's Guide"

Chapter 2: "How Kerberos Works".