DirectAccess and Always On VPN with Trusted Platform Module (TPM) Certificates

DirectAccess and Always On VPN with Trusted Platform Module (TPM) CertificatesTo enhance security when provisioning certificates for DirectAccess (computer) or Windows 10 Always On VPN (user) it is recommended that private keys be stored on a Trusted Platform Module (TPM) on the client device. A TPM is a dedicated security processor included in nearly all modern computers. It provides essential hardware protection to ensure the highest levels of integrity for digital certificates and is used to generate, store, and restrict the use of cryptographic keys. It also includes advanced security and protection features such as key isolation, non-exportability, and anti-hammering to prevent brute-force attacks.

To ensure that private keys are created and stored on a TPM, the certificate template must be configured to use the Microsoft Platform Crypto Provider. Follow the steps below to configure a certificate template required to use a TPM.

  1. Open the Certificate Templates management console (certtmpl.msc) and duplicate an existing certificate template. For example, if creating a certificate for DirectAccess, duplicate the Workstation Authentication certificate template. For Always On VPN, duplicate the User certificate template.
  2. On the Compatibility tab, ensure the Certification Authority and Certificate recipient compatibility settings are set to a minimum of Windows Server 2008 and Windows Vista/Server 2008, respectively.DirectAccess and Always On VPN with Trusted Platform Module (TPM) Certificates
  3. Select the Cryptography tab.
  4. Choose Key Storage Provider from the Provider Category drop down list.
  5. Choose the option Requests must use one of the following providers and select Microsoft Platform Crypto Provider.DirectAccess and Always On VPN with Trusted Platform Module (TPM) Certificates

Note: If Microsoft Platform Crypto Provider does not appear in the list above, got to the Request Handling tab and uncheck the option Allow private key to be exported.

Complete the remaining certificate configuration tasks (template display name, subject name, security settings, etc.) and publish the certificate template. Client machines configured to use this template will now have a certificate with private key fully protected by the TPM.

Additional Resources

Trusted Platform Module (TPM) Fundamentals

DirectAccess and Always On VPN Certificate Auto Enrollment

DirectAccess Manage Out with ISATAP and NLB Clustering

DirectAccess Manage Out with ISATAP and NLB ClusteringDirectAccess connections are bidirectional, allowing administrators to remotely connect to clients and manage them when they are out of the office. DirectAccess clients use IPv6 exclusively, so any communication initiated from the internal network to remote DirectAccess clients must also use IPv6. If IPv6 is not deployed natively on the internal network, the Intrasite Automatic Tunnel Addressing Protocol (ISATAP) IPv6 transition technology can be used to enable manage out.

ISATAP Supportability

According to Microsoft’s support guidelines for DirectAccess, using ISATAP for manage out is only supported for single server deployments. ISATAP is not supported when deployed in a multisite or load-balanced environment.

Not supported” is not the same as “doesn’t work” though. For example, ISATAP can easily be deployed in single site DirectAccess deployments where load balancing is provided using Network Load Balancing (NLB).

ISATAP Configuration

To do this, you must first create DNS A resource records for the internal IPv4 address for each DirectAccess server as well as the internal virtual IP address (VIP) assigned to the cluster.

DirectAccess Manage Out with ISATAP and NLB Clustering

Note: Do NOT use the name ISATAP. This name is included in the DNS query block list on most DNS servers and will not resolve unless it is removed. Removing it is not recommended either, as it will result in ALL IPv6-enabled hosts on the network configuring an ISATAP tunnel adapter.

Once the DNS records have been added, you can configure a single computer for manage out by opening an elevated PowerShell command window and running the following command:

Set-NetIsatapConfiguration -State Enabled -Router [ISATAP FQDN] -PassThru

DirectAccess Manage Out with ISATAP and NLB Clustering

Once complete, an ISATAP tunnel adapter network interface with a unicast IPv6 address will appear in the output of ipconfig.exe, as shown here.

DirectAccess Manage Out with ISATAP and NLB Clustering

Running the Get-NetRoute -AddressFamily IPv6 PowerShell command will show routes to the client IPv6 prefixes assigned to each DirectAccess server.

DirectAccess Manage Out with ISATAP and NLB Clustering

Finally, verify network connectivity from the manage out host to the remote DirectAccess client.

Note: There is a known issue with some versions of Windows 10 and Windows Server 2016 that may prevent manage out using ISATAP from working correctly. There’s a simple workaround, however. More details can be found here.

Group Policy Deployment

If you have more than a few systems on which to enable ISATAP manage out, using Active Directory Group Policy Objects (GPOs) to distribute these settings is a much better idea. You can find guidance for creating GPOs for ISATAP manage out here.

DirectAccess Client Firewall Configuration

Simply enabling ISATAP on a server or workstation isn’t all that’s required to perform remote management on DirectAccess clients. The Windows firewall running on the DirectAccess client computer must also be configured to securely allow remote administration traffic from the internal network. Guidance for configuring the Windows firewall on DirectAccess clients for ISATAP manage out can be found here.

ISATAP Manage Out for Multisite and ELB

The configuration guidance in this post will not work if DirectAccess multisite is enabled or external load balancers (ELB) are used. However, ISATAP can still be used. For more information about enabling ISATAP manage out with external load balancers and/or multisite deployments, fill out the form below and I’ll provide you with more details.

Summary

Once ISATAP is enabled for manage out, administrators on the internal network can remotely manage DirectAccess clients wherever they happen to be. Native Windows remote administration tools such as Remote Desktop, Windows Remote Assistance, and the Computer Management MMC can be used to manage remote DirectAccess clients. In addition, enterprise administration tools such as PowerShell remoting and System Center Configuration Manger (SCCM) Remote Control can also be used. Further, third-party remote administration tools such as VNC, TeamViewer, LogMeIn, GoToMyPC, Bomgar, and many others will also work with DirectAccess ISATAP manage out.

Additional Information

ISATAP Recommendations for DirectAccess Deployments

DirectAccess Manage Out with ISATAP Fails on Windows 10 and Windows Server 2016 

DirectAccess Client Firewall Rule Configuration for ISATAP Manage Out

DirectAccess Manage Out and System Center Configuration Manager (SCCM)

Contact Me

Interested in learning more about ISATAP manage out for multisite and external load balancer deployments? Fill out the form below and I’ll get in touch with you.

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Outlook Offline over DirectAccess on Windows 10

Outlook Offline over DirectAccess on Windows 10You may encounter a scenario in which Outlook on Windows 10 reports that it is working offline while connected remotely via DirectAccess. The Network Connectivity Status Indicator (NCSI) shows DirectAccess is in a connected state and all other internal resources are accessible.

Outlook Offline over DirectAccess on Windows 10

This is caused by the default settings of the IP-HTTPS tunnel interface on the DirectAccess server not advertising a default route for connected DirectAccess clients. To resolve this issue, enable default route advertising for IP-HTTPS on each DirectAccess server in the enterprise by running the following PowerShell command.

Get-NetIPInterface | Where-Object {$_.InterfaceAlias -eq “IPHTTPSInterface”} | Set-NetIPInterface -AdvertiseDefaultRoute Enabled -PassThru

Outlook Offline over DirectAccess on Windows 10

In the past I’ve heard reports of this setting being overwritten after group policy refresh. Recent testing on Windows Server 2016 does not show this behavior, however. Please report any results you may have in the comments below. Thanks!