Disabling Unused IPv6 Transition Technologies for DirectAccess Clients

From a client perspective, DirectAccess is an IPv6-only solution and requires IPv6 connectivity end to end. To enable the solution to work on IPv4-only networks, DirectAccess makes use of one of several IPv6 transition technologies – 6to4, Teredo, or IP-HTTPS. By leveraging these IPv6 transition technologies, a DirectAccess client can communicate with the DirectAccess server when they are both connected to the public IPv4 Internet, which is the most common deployment scenario today.

The first two IPv6 transition technologies, 6to4 and Teredo, both require that the DirectAccess server be directly connected to the public Internet. Beginning with Windows Server 2012, placing the DirectAccess server behind a border router or edge firewall performing Network Address Translation (NAT) is now supported. However, in this deployment model only the IP-HTTPS IPv6 transition protocol can be utilized. In this scenario, it is recommended to disable the unused IPv6 transition protocols to prevent potential connectivity issues. You can disable them on a per-host basis using PowerShell, which is fine for individual client testing purposes, or globally using Active Directory Group Policy Objects (GPOs), which is recommend for enterprise-wide production deployment.

To disable unused IPv6 transition protocols on a per-host basis on Windows 8 clients using PowerShell, open an elevated PowerShell prompt and execute the following commands:

Set-Net6to4Configuration –State disabled
Set-NetTeredoConfiguration –Type disabled
Set-NetIsatapConfiguration –State disabled

To disable unused IPv6 transition protocols on a per-host basis on Windows 7 client using netsh, open an elevated command prompt and execute the following commands:

netsh interface 6to4 set state disabled
netsh interface teredo set state disabled
netsh interface isatap set state disabled

To disable unused IPv6 transition protocols using Active Directory GPO, open the Group Policy Management Console (GPMC) and create a new GPO. Edit the GPO by navigating to Computer Configuration / Policies / Administrative Templates / Network / TCP/IP Settings / IPv6 Transition. Double-click Set 6to4 State and enable the policy, then select Disabled State from the list of states. Repeat these steps for Teredo and ISATAP.

Disable DirectAccess IPv6 Transition Protocol using GPO

Change the security filtering for the GPO and specify the security group for your DirectAccess clients. Once complete, link the new GPO to the domain.

Disable DirectAccess IPv6 Transition Protocol using GPO

As a reminder, the steps above are for disabling unused IPv6 transition protocols in a deployment scenario where the DirectAccess server is running Windows Server 2012/R2 and is deployed behind a NAT device. If your DirectAccess server is connected directly to the public Internet, disabling these IPv6 transition protocols is not required.

Microsoft Security Update MS13-064 and DirectAccess

With the August security update release cycle, Microsoft issued security bulletin MS13-064 to address a vulnerability in the Windows NAT driver that could result in a denial of service. The vulnerability could be exploited by an attacker who sends a specially crafted ICMP packet to the server running the Windows NAT Driver service. The vulnerability exists only on Windows Server 2012 and the affected driver, winnat.sys, is present when the DirectAccess role is installed. This vulnerability only affects only full installations of Windows Server 2012. Windows Server 2012 Core is not affected. If you are running DirectAccess on a full installation of Windows Server 2012, make sure you install this update as soon as possible to be protected from potential denial of service attacks. For more information about this update, click here. For a comprehensive list of updates that apply to DirectAccess on Windows Server 2012 as well as previous versions, please refer to Jason Jones’ DirectAccess hotfix summary page.

Windows 8.1 DirectAccess Connection Properties

Microsoft recently announced the availability of Windows 8.1 Enterprise preview. If you’ve downloaded the software to evaluate DirectAccess, you may be wondering where the DirectAccess connection properties have gone. In Windows 8, the DirectAccess connection properties can be accessed by pressing Window Key + I, clicking the active network icon, and then right-clicking Workplace Connection.

DirectAccess Connection Properties

DirectAccess Connection Properties

To access the DirectAccess connection properties in Windows 8.1, press Window Key + I, click Change PC Settings, and then click Network.

Highlight Connections and click Workplace Connection.

Highlight Connections and click Workplace Connection.

Highlight Connections and click Workplace Connection.

Highlight Connections and click Workplace Connection.

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