You install Microsoft Forefront Threat Management Gateway (TMG) 2010 on two servers.
You set up a site-to-site VPN connection between the two servers. For example, you set up a PPTP or a L2TP/IPsec connection.
The line for the connection recovers from a disruption.
In this scenario, the PPTP or L2TP/IPsec connection is not reestablished between the two servers.
This issue occurs because the new allocated address is not added to the network when the unicast address of the dial-out adapter is not available.
The network snapshot contains the dial-out adapter in reconnection. The adapter information is from an in-memory snapshot of IPHelper. However, the retrieval of unicast addresses is from IPHelper. Therefore, a reconnection does not occur when the in-memory snapshot does not contain current adapter information.
To resolve this issue, install the software update that is described in the following Microsoft Knowledge Base (KB) article:
2498770 Software Update 1 rollup 3 for Forefront Threat Management Gateway (TMG) 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates
TMG 2010: After Line disruptions the tunnel does not re-establish for PPTP or L2TP/ipsec between two TMG servers