Original Location:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q239924
The information in this article applies to:
Windows contains the "Media Sensing" feature. You may use this feature on a
Windows-based computer using Transmission Control Protocol/Internet Protocol
(TCP/IP) to detect whether or not your network media is in a "link state". A
"link state" is defined as the physical media connecting or inserting itself on
the network. For example, assuming a 10bt or 100bt physical media, Ethernet
network adapters and hubs typically have a "link" light to indicate the current
connection status. This is the same condition in which Windows can detect a
link. Whenever Windows detects a "down" state on the media, it removes the bound
protocols from that adapter until it is detected as "up" again. There may be
situations where you may not want your network adapter to detect this state, and
you can configure this by editing the registry.
NOTE : 10b2 or coaxial (RG-58) Ethernet cable is not a connection-based
media. Because of this, Windows does not attempt to detect a "connect" state if
this type of cabling is used.
WARNING : Using Registry Editor incorrectly can cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that problems resulting from the incorrect use of Registry Editor can
be solved. Use Registry Editor at your own risk.
For information about how to edit the registry, view the "Changing Keys and
Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete
Information in the Registry" and "Edit Registry Data" Help topics in
Regedt32.exe. Note that you should back up the registry before you edit it. If
you are running Windows NT or Windows 2000, you should also update your
Emergency Repair Disk (ERD).
To prevent your network adapter from detecting the link state:
NOTE : NetBEUI and IPX do not recognize Media Sense.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters
Add the following registry value:
Value Name: DisableDHCPMediaSense
Data Type: REG_DWORD -Boolean
Value Data Range: 0, 1 (False, True) Default: 0 (False)
Description: This parameter controls DHCP Media Sense behavior. If you set
this value data to 1, DHCP, and even non-DHCP, clients ignore Media Sense
events from the interface. By default, Media Sense events trigger the DHCP
client to take an action, such as attempting to obtain a lease (when a connect
event occurs), or invalidating the interface and routes (when a disconnect
event occurs).
NOTE : There are some side effects of disabling the "Media Sensing"
feature. For example, if you have a machine with two network adapters, and you
have the "Media Sensing" feature enabled, if one network adapter does not work,
it is unbound, and associated routes are removed so that all traffic goes
through the other network adapter (assuming a default gateway is there). Also,
if you are a roaming (portable) user, the "Media Sensing" feature is what
provides the ability to connect to any network and have everything work, without
restarting, release and renewing, and so on. After disabling Media Sense and
restarting, Windows still shows the "Network Disconnected" icon on the TaskBar
and the 'ipconfig' command still shows a "Media State .....: Cable Disconnected"
message when the cable is disconnected. However, the Network Interface is bound
to TCP/IP and you can verify this by looking at the route table --you can use
the "route print" command-- which shows the interface IP address (you are also
able to ping the IP address assigned to the NIC).
| Published | Aug 31 1999 4:10PM | Issue Type | kbhowto |
| Last Modifed | Feb 19 2002 5:56PM | Additional Query Words | |
| Keywords | kbnetwork kbtool | ||