Windows 2000 PDC Emulator's CPU Spikes When Large Number of KRB_AS_REQs Are Sent from the BDC

The primary domain controller (PDC) emulator's CPU(s) may show a sustained high usage. This may be caused by a large number of Kerberos Authentication Server requests (KRB_AS_REQs) that contain a bad password being sent from domain controllers in the domain. To verify that this is the case, capture the traffic to the PDC Emulator by using Network Monitor.

This situation typically occurs for two reasons:

• A user changes his or her password on one computer but is logged on to another computer with the expired password. The computer with the expired password attempts to renew its Ticket Granting Ticket (TGT) from a Key Distribution Center (KDC) by using its old password. The KDC (whichever domain controller receives the request) realizes that the password is not the same one it has, so it attempts to verify the password against the PDC emulator, sending numerous KRB_AS_REQs.
• A less common cause is a user typing the wrong password. The problem is in the KDC in Kerberos version 5 authentication on the domain controller.

To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

This problem was first corrected in Windows 2000 Service Pack 1.

When a password is changed, it is changed on the logon domain controller, and then the password change is sent to the PDC emulator. Because of this, the PDC emulator must be checked when an incorrect password is used. Otherwise, the user may change a password, and if the user is validated by a different domain controller than the one on which the password change occurred, the password change may not yet have been replicated to that domain controller. Therefore, the PDC emulator must be checked. For additional information, click the article number below to view the article in the Microsoft Knowledge Base: For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the article number below to view the article in the Microsoft Knowledge Base: