Windows Vista does not keep its DHCP IP address if a DHCP server is not available

Important This article contains information about how to modify the registry. Make sure that you 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:

If a Windows Vista-based Dynamic Host Configuration Protocol (DHCP) client computer is restarted and if the DHCP Server service is not available, the client will not maintain a valid lease. Therefore, you cannot access some network resources.

In this scenario, the computer loses the IP address that was assigned to it by the DHCP server even though the default gateway is available. Instead, an Automatic Private IP Addressing (APIPA) address, such as 169.254.0.1, is assigned to the client computer. Or, if the adapter was assigned an IP address by using the Alternative Configuration tab for the adapter, the adapter will use this address.

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 the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To resolve this issue, add a registry value to force the client to keep its DHCP IP address, even if a DHCP server is not available. The registry value does not exist by default. You have to add it. To do this, follow these steps:

1. Open Registry Editor. To do this, click Start, type regedit in the Start Search box, and then press ENTER.
2. If you want to activate the setting for all adapters, locate the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
   Or, if you want to activate this setting for a specific adapter, locate the adapter-specific registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<Adapter>
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type DontPingGateway, and then press ENTER.
5. On the Edit menu, click Modify.
6. In the Value data box, type 1, and then click OK.
7. Exit Registry Editor.
8. Restart the computer.

This procedure forces the client to keep its DHCP IP address, even if a DHCP server is not available. If you use the Alternate Configuration tab to modify the IP address for an adapter, this IP address is assigned to the adapter.