After you have connected a Vista based computer to a network that supports dynamix Host Configuration Protocol or DHCP you are unable to contect to the network. The router or the other device may not support the DHCP Broadcast flag.

This issue will occur because with XP SP2 the Broadcast flag in DHCP is set to 0 (meaning disabled), with Windows Vista the Broadcast flag is not disabled and therefore some non Microsoft  DHCP servers cannot process the the DHCP discovery packets. This can happen on some routers as well.

FIX:  (WARNING!! takes no responsibility for your actions)  We will be editing the registry.  Backup your data before proceeding in-case something goes wrong.

Click the Windows Start Button, in the start search box type regedit. In the programs list select Regedit.  You may be prompted for the admin password.

Now Locate and then click the following registry subkey:


In this registry path, click the (GUID) subkey that corresponds to the network adapter that is connected to the network. On the Edit menu, point to New, and then click DWORD (32-bit) Value.
In the New Value #1 box, type DhcpConnDisableBcastFlagToggle, and then press ENTER.
Right-click DhcpConnDisableBcastFlagToggle, and then click Modify.

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

Close Registry Editor.

Reboot your computer.  If you did it right then Vista will now not broadcast a DHCP Broadcast flag.

If the router or the non-Microsoft DHCP server does not support the DHCP BROADCAST flag, you can set the following registry entry as follows:


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

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