Assume that a client uses an IP address in which the end octet is .255. For example, a client is configured to use IP Address 10.1.1.255. In this situation, client traffic is blocked as "spoofed" in a Microsoft Forefront Threat Management Gateway 2010 environment.
To resolve this problem, install the service pack that is described in the following Microsoft Knowledge Base article:
2555840 Microsoft Forefront Threat Management Gateway 2010 Service Pack 2
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