Select the product you need help with
- Internet Explorer
- Windows Phone
- More products
How to configure an L2TP/IPsec server behind a NAT-T device in Windows Vista and in Windows Server 2008
Article ID: 926179 - View products that this article applies to.
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:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
By default, Windows Vista and the Windows Server 2008 operating system do not support Internet Protocol security (IPsec) network address translation (NAT) Traversal (NAT-T) security associations to servers that are located behind a NAT device. Therefore, if the virtual private network (VPN) server is behind a NAT device, a Windows Vista-based VPN client computer or a Windows Server 2008-based VPN client computer cannot make a Layer Two Tunneling Protocol (L2TP)/IPsec connection to the VPN server. This scenario includes VPN servers that are running Windows Server 2008 and Microsoft Windows Server 2003.
Because of the way in which NAT devices translate network traffic, you may experience unexpected results when you put a server behind a NAT device and then use an IPsec NAT-T environment. Therefore, if you must have IPsec for communication, we recommend that you use public IP addresses for all servers that you can connect to from the Internet. However, if you have to put a server behind a NAT device and then use an IPsec NAT-T environment, you can enable communication by changing a registry value on the VPN client computer and the VPN server.
To create and configure the
AssumeUDPEncapsulationContextOnSendRuleregistry value, follow these steps:
For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/818043/ )L2TP/IPsec NAT-T update for Windows XP and Windows 2000
(http://support.microsoft.com/kb/885348/ )IPSec NAT-T is not recommended for Windows Server 2003 computers that are behind network address translators
Article ID: 926179 - Last Review: March 15, 2007 - Revision: 2.6