How to Disable Microsoft CHAP Authentication (238734)

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SYMPTOMS

When you use Microsoft Routing and Remote Access Service (RRAS) as a Remote Authentication Dial-In User Service (RADIUS) client, you can selectively enable or disable Microsoft Challenge Handshake Authentication Protocol (CHAP) authentication by setting the OfferMSCHAP registry value.

If the host or router that is attempting to dial in does not support Microsoft CHAP and does not correctly implement RFC 1331, you may observe delays during authentication that lead to an unsuccessful Point-to-Point Protocol (PPP) connection because of Link Control Protocol (LCP) timeouts.

RESOLUTION

Windows NT Server or Workstation 4.0

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:

http://www.microsoft.com/windows/servicepacks/ -or-
152734how to obtain the latest windows nt 4.0 service pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/directory/overview.asp

Windows NT Server 4.0, Terminal Server Edition

To resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack

STATUS

Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition.

This problem was first corrected in Windows NT Server 4.0 Service Pack 6 and Windows NT Server 4.0, Terminal Server Edition Service Pack 6.

MORE INFORMATION

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Because of a change made to an existing configurable parameter, you can disable Microsoft CHAP authentication whether or not your RRAS server is operating as a RADIUS client. To disable Microsoft CHAP:

Start Registry Editor (Regedt32.exe).
Locate the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\PPP\CHAP
On the Edit menu, click Add Value, and then add the following registry value:
DWORD: OfferMSCHAP
Value: 0x00000000
Quit Registry Editor.

After you add this value, Microsoft CHAP is not offered to PPP clients.