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Certain routers or DHCP servers are incompatible with Windows Vista. This article helps you resolve the issue. If you are not sure if your router is compatible, you can still try the fix.

Fix it automatically

Click "Fix this problem" to automatically fix this issue. Click Run in the File Download dialog box, and then follow the steps in the Fix it wizard.


  • This wizard may be only in English. However, the automatic fix also works for other language versions of Windows.

  • If you are not on the computer that has the problem, save the Fix it solution to a flash drive or a CD, and then run it on the computer that has the problem.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in WindowsTo resolve this issue yourself, disable the DHCP BROADCAST flag in Windows Vista. To do this, follow these steps:

  1. Click Start Start button , type regedit in the Start Search box, and then click regedit in the Programs list.

     User Account Control permission  If you are prompted for an administrator password or for confirmation, type the password or provide confirmation.

  2. Locate the following register node:
    HKEY_LOCAL_MACHINE > SOFTWARE > Microsoft > WindowsNT > CurrentVersion > NetworkCards > <number>

  3. Look at each number that is listed under the NetworkCards node in order to find the network adapter GUID. On the right side, the Description item lists the network adapter and the ServiceName item lists the corresponding GUID. Remember this GUID.

  4. Locate and then click the following registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{<Network Adapter GUID>}In this registry path, click the <Network Adapter GUID> subkey that corresponds to the network adapter that is connected to the network.
    Note Network Adapter GUID  is a placeholder for the network adapter GUID in this article. To find the corresponding GUID, refer to step 2 and step 3.

  5. On the Edit menu, point to New, and then click DWORD (32-bit) Value.

  6. In the New Value #1 box, type DhcpConnEnableBcastFlagToggle, and then press ENTER.

  7. Right-click DhcpConnEnableBcastFlagToggle, and then click Modify.

  8. In the Value data box, type 1, and then click OK.

  9. Close Registry Editor.

When you set this registry key to 1, Windows Vista first tries to obtain an IP address by using the BROADCAST flag in DHCP Discover packets. If that fails, Windows Vista tries to obtain an IP address without using the BROADCAST flag in DHCP Discover packets.


By default, the BROADCAST flag in DHCP discovery packets is enabled in Windows Vista (DhcpConnEnableBcastFlagToggle = 1). Therefore, Windows Vista gets an IP address by using the BROADCAST flag in DHCP discovery packets. If a router or DHCP server can’t process the DHCP discovery packets, Windows Vista will fail to get an IP address. The fix disables the BROADCAST flag by setting DhcpConnEnableBcastFlagToggle to 0.

By default, this problem does not exist in Windows XP Service Pack 2, Windows XP Service Pack 3 or Windows 7 because the BROADCAST flag is disabled (DhcpConnEnableBcastFlagToggle = 0).

More Information

If you know the router or the non-Microsoft DHCP server does not support the DHCP BROADCAST flag, you can configure the following values for the following registry entry instead of using the DhcpConnEnableBcastFlagToggle registry key.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{<Network Adapter GUID>}

Value name: DhcpConnForceBroadcastFlag
Value type: REG_DWORD
Value data: 0 Notes

  • A value of 0 disables the registry entry. You can use this value to prevent Windows Vista from using the DHCP BROADCAST flag. After you configure the registry entry, Windows Vista never uses the DHCP BROADCAST flag.

  • This issue does not occur in Windows 7. By default, DhcpConnEnableBcastFlagToggle is set to 1.

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