You cannot browse Web servers on a remote site when you use IPsec tunnels to connect sites on a Windows Server 2003-based computer that is running ISA Server 2004, ISA Server 2006, or Forefront Threat Management Gateway, Medium Business Edition

You are using Internet Protocol security (IPsec) tunnels to connect remote sites to each other on a Windows Server 2003-based computer that is running Microsoft Internet Security and Acceleration (ISA) Server 2004 or ISA Server 2006, or on a Windows Server 2008-based computer that is running Microsoft Forefront Threat Management Gateway, Medium Business Edition. When you or a user on another computer try to browse Web servers on the remote sites through the IPsec tunnels, you cannot browse the Web servers. All other traffic crosses the tunnels to and from the remote sites correctly.

This behavior may occur if you use a non-primary IP address as the local endpoint for an IPSec tunnel that connects the remote site networks. The following configurations are not supported in ISA Server 2004, in ISA Server 2006, or in Microsoft Forefront Threat Management Gateway, Medium Business Edition:

• Network address translation (NAT) cannot be used as part of the connection between an internal network and a remote site network. Network traffic that is initiated from an internal network to a remote site network will not connect as expected.
• A Web Proxy cannot be used as part of the connection between an internal network and a remote site network.

To resolve this behavior, follow these steps:

1. When you connect multiple IPsec remote site networks to the same computer that is running ISA Server 2004, ISA Server 2006, or Microsoft Forefront Threat Management Gateway, Medium Business Edition, define a unique IP address for each local endpoint of each IPsec tunnel on the remote site networks.
   
   For additional information about how to define a unique IP address for the local endpoint of an IPSec tunnel, visit the "To specify an IPsec tunnel" Web page on the following Microsoft Web site:
   http://technet2.microsoft.com/windowsserver/en/library/8C7F14B7-6A1A-45FE-B10B-DA9EEDA4A7351033.mspx (http://technet2.microsoft.com/windowsserver/en/library/8C7F14B7-6A1A-45FE-B10B-DA9EEDA4A7351033.mspx)
2. HTTP traffic can be enabled by defining a new protocol that is not configured for the Web Proxy application filter. For example, define a new protocol named HTTP1. Use the new protocol in a rule that enables HTTP traffic to the specific remote site network. If multiple IPsec remote site networks require NAT/HTTP functionality, use a dedicated network adaptor for each remote site network. Use the primary IP address on the network adaptor as the local endpoint.
   
   For more information about how to create a protocol definition on ISA Server 2004 and on ISA Server 2006, visit the "To create a protocol definition" Web page on the following Microsoft Web site:
   http://technet.microsoft.com/en-us/library/bb838964.aspx (http://technet.microsoft.com/en-us/library/bb838964.aspx)
   For more information about how to create a protocol definition on Microsoft Forefront Threat Management Gateway, Medium Business Edition, visit the following Microsoft Web site:
   http://technet.microsoft.com/en-us/library/cc441512.aspx (http://technet.microsoft.com/en-us/library/cc441512.aspx)

For more information about connecting remote sites, visit the "Connecting Remote Sites" Web page on the following Microsoft Web site: For more information about IPSec Tunneling, visit the "What Is IPSec Tunneling?" Web page on the following Microsoft Web site: For more information about site-to-site VPN on Forefront Threat Management Gateway, visit the following Microsoft Web site: