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.
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.
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.