An IPsec VPN site-to-site tunnel or a PPTP VPN site-to-site tunnel does not work if you enable integrated NLB on a Forefront TMG 2010 array

Symptoms

Consider the following scenario:

• You configure an Internet Protocol Security (IPsec) VPN site-to-site tunnel or a Point-to-Point Tunneling Protocol (PPTP) VPN site-to-site connection between a Microsoft Forefront Threat Management Gateway (TMG) 2010 multiple-member array deployment and another site. And, you can successfully access resources through the tunnel.

• You enable integrated network load balancing (NLB) on the TMG 2010 array.

• You try to access resources in another site.

In this scenario, the IPsec tunnel does not work, and you cannot access resources on either side of the tunnel.

Note The scope of this problem is actually larger than IPsec site-to-site VPN. The problem that is described here may occur in any array-based TMG 2010 deployments for which integrated NLB is enabled when NLB WMI events such as node convergence are triggered. Site-to-site VPN that has NLB enabled is the most visible example.

Cause

This problem occurs because TMG 2010 incorrectly defines discretionary access control lists (DACLs) for the COM services that are exposed by TMG 2010. These DACLs prevent NLB WMI event notifications from being accepted by TMG services. Therefore, the internal NLB state of TMG is not updated, and subcomponents that depend on the NLB state, such as IPsec filter definitions, are not initialized correctly.

Resolution

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Forefront TMG 2010 Service Pack 1.