Microsoft KB Archive/239924

= How to disable the Media Sensing feature for TCP/IP in Windows =

Article ID: 239924

Article Last Modified on 11/13/2006

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
 * Microsoft Windows Server 2003, Web Edition
 * Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
 * Microsoft Windows XP Professional x64 Edition
 * Microsoft Windows XP for Itanium-based Systems Version 2003
 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Media Center Edition 2002
 * Microsoft Windows XP Media Center Edition 2004
 * Microsoft Windows XP Professional
 * Microsoft Windows XP Tablet PC Edition
 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Datacenter Server
 * Microsoft Windows 2000 Professional Edition
 * Microsoft Systems Management Server 2003
 * Microsoft Systems Management Server 2.0 Standard Edition

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This article was previously published under Q239924



Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SUMMARY
On a Windows-based computer that uses TCP/IP, you can use the Media Sensing feature to detect whether the network media are in a link state. Ethernet network adapters and hubs typically have a "link" light that indicates the connection status. This status is the same condition that Windows interprets as a link state. Whenever Windows detects a "down" state, it removes the bound protocols from that adapter until it is detected as "up" again. Sometimes, you may not want the network adapter to detect this state. You can set this configuration by modifying the registry.

Note 10B2 coaxial (RG-58) Ethernet cable is not a connection-based medium. Therefore, Windows does not try to detect a link state when this kind of cabling is used.



MORE INFORMATION
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To prevent the network adapter from detecting a link state, follow these steps.

Note The NetBEUI protocol and the IPX protocol do not support Media Sensing.  Start Registry Editor. Locate the following registry subkey:

 Add the following registry entry to the  subkey:

Name: DisableDHCPMediaSense

Data type: REG_DWORD (Boolean)

Value: 1

Note This entry controls the behavior of Media Sensing. By default, Media Sensing events trigger a DHCP client to take an action. For example, when a connect event occurs, the client tries to obtain a lease. When a disconnect event occurs, the client may invalidate the interface and routes. If you set this value data to 1, DHCP clients and non-DHCP clients ignore Media Sensing events. Restart the computer.

Note Microsoft Windows Server 2003 supports Media Sensing when it is used in a server cluster environment. By default, however, Media Sensing is disabled in a Windows Server 2003-based server cluster, and the DisableDHCPMediaSense registry entry has no effect. In Windows Server 2003 Service Pack 1 (SP1), the DisableClusSvcMediaSense registry entry was introduced. You can use this registry entry to enable Media Sensing on the Windows Server 2003-based nodes of a server cluster. The details of the DisableClusSvcMediaSense registry entry are as follows:

Key: HKEY_LOCAL_MACHINE\Cluster\Parameters

Name: DisableClusSvcMediaSense

Data type: REG_DWORD (Boolean)

Default value: 0

By default, the DisableClusSvcMediaSense entry is set to 0. When this entry is set to 0, Media Sensing is disabled. If you set the DisableClusSvcMediaSense entry to 1, you can use the DisableDHCPMediaSense entry to enable Media Sensing. This behavior matches the behavior of a Microsoft Windows 2000 Server cluster environment.

Keywords: kbhowto kbnetwork KB239924

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