DirectAccess Consulting Services Now Available

Microsoft Certified Solutions Associate (MCSA)For the last five years I’ve been helping organizations large and small deploy DirectAccess. During that time I have amassed a wealth of knowledge and experience with this unique technology. DirectAccess is not trivial to install, configure, or troubleshoot. Also, it’s easy to make mistakes in the planning and design phase that can turn in to serious issues later in the deployment. To make matters worse, many organizations are deploying DirectAccess for the first time, and without essential guidance they are prone to making common mistakes or choosing configuration options that are less than optimal both in terms of supportability and performance.

Having deployed DirectAccess for some of the largest companies in the world, there isn’t much I haven’t already encountered. If you are looking for the best chance of success for your DirectAccess deployment, consider a consulting engagement with me. I can provide assistance with all facets of DirectAccess implementation including planning and design, installation, configuration, and troubleshooting. Consulting services at reasonable rates are available for all types of DirectAccess work including:

  • New DirectAccess installations
  • Migration from previous versions of DirectAccess
  • Upgrade or expansion of existing DirectAccess deployment
  • Enterprise planning and design for large-scale, multisite DirectAccess deployments
  • DirectAccess high availability (local and geographic)
  • Manage-out for DirectAccess with external hardware load balancers and/or multisite configuration
  • Multisite DirectAccess with geographic redundancy for Windows 7 clients
  • Existing DirectAccess design review and security assessment
  • Windows Server 2012 R2 client-based VPN configuration
  • DirectAccess client connectivity troubleshooting
  • DirectAccess training

Additionally, consulting services are available for a variety of security solutions as well as on-premises and cloud networking technologies such as:

  • Azure networking and infrastructure
  • Cross-premises connectivity to Azure
  • Certificate services (PKI)
  • IP address management
  • ISA Server and Forefront Threat Management Gateway (TMG) migration

All services can be performed on-site or remotely. If you are interested in obtaining my services, fill out the form below and I’ll contact you.

DirectAccess DNS Records Explained

After installing and configuring DirectAccess with Windows Server 2012 R2, several new host records appear automatically in the internal DNS (assuming dynamic DNS is supported, of course). One of them is directaccess-corpConnectivityHost and the other is directaccess-WebProbeHost. These DirectAccess DNS entries are used by Windows 8 and later clients for connectivity checks at various stages of DirectAccess connection establishment.

DirectAccess DNS Records Explained

Figure 1 – DirectAccess DNS records for IPv4-only network.

DirectAccess DNS Records Explained

Figure 2 – DirectAccess DNS records for dual-stack IPv4/IPv6 network.

Here is a detailed description for each of these DirectAccess DNS entries.

directaccess-corpConnectivityHost – This DNS host record includes both A and AAAA records when deployed on IPv4-only networks. Its A host record resolves to 127.0.0.1, which is the IPv4 loopback address. Its AAAA host record resolves to an IPv6 address that is a combination of the DirectAccess NAT64 IPv6 prefix and 7F00:1 (the hexadecimal equivalent of 127.0.0.1). When DirectAccess is configured on a network with native IPv6, the directaccess-corpConnectivityHost DNS record will only include a single AAAA record resolving to ::1.

This host record is used by the DirectAccess client to determine if name resolution for the corporate namespace is working after the IPv6 transition tunnel (6to4, Teredo, or IP-HTTPS) has been established. It does this by attempting to resolve the hostname directaccess-corpConnectivityHost.<corp_fqdn> (e.g. directaccess-corpConnectivityHost.corp.example.net) to an IPv6 address that it expects (the organization’s NAT64 prefix + 7F00:1 or ::1). If it does not resolve, or resolves to a different address, the client will assume that the transition tunnel was not established successfully and, if possible, fall back to another IPv6 transition protocol and repeat the process until it is successful.

Note: The DirectAccess client does not attempt to connect to the IP address resolved by directaccess-corpConnectivityHost. It simply compares the IP address returned by the query to the expected address (NAT64 prefix + 7F00:1 or ::1).

directaccess-WebProbeHost – This DNS host record includes only A records and resolves to the IPv4 address assigned to the internal network interface of the DirectAccess server. If load balancing is enabled, this host record will resolve to the virtual IP address (VIP) of the array. For multisite deployments there will be directaccess-WebProbeHost A host records for each entry point in the organization.

This host record is used by the DirectAccess client to verify end-to-end corporate network connectivity over the DirectAccess connection. The client will attempt to connect to the directaccess-WebProbeHost URL using HTTP. If successful, the DirectAccess connectivity status indicator will show Connected.

If any of these DirectAccess DNS records are missing or incorrect, a number of issues may arise. If the directaccess-corpConnectivityHost host record is missing or incorrect, DirectAccess IPv6 transition tunnel establishment may fail. If the directaccess-WebProbeHost record is missing or incorrect, the DirectAccess connectivity status indicator will perpetually show Connecting. This commonly occurs when an external load balancer is used and a virtual server isn’t created for the web probe host port (TCP 80). In addition, these DirectAccess DNS entries are not static and may be deleted if DNS scavenging of stale resource records is enabled on the DNS server.

Enable Teredo Support after DirectAccess Has Been Configured

DirectAccess leverages IPv6 transition protocols to enable clients to connect to the DirectAccess server when both are located on the IPv4 Internet. When the DirectAccess server is located in a perimeter or DMZ network behind a NAT device, only the IP-HTTPS IPv6 transition protocol is used. When the DirectAccess server is edge facing with public IPv4 addresses assigned to the external interface, the 6to4 and Teredo IPv6 transition protocols are also supported.

Note: It is generally recommended that the 6to4 IPv6 transition protocol be proactively disabled. More details here.

To support Teredo, the DirectAccess server must be configured with two consecutive public IPv4 addresses. When you configure DirectAccess for the first time, Teredo will automatically be configured if the installation detects the proper requirements for it. If you neglect to add the second consecutive public IPv4 address to the external network interface and configure DirectAccess, the installation will complete successfully without enabling Teredo support and Teredo will not appear in the list of services operations status, as shown here.

Enable Teredo Support after DirectAccess Has Been Configured

To enable Teredo support after you’ve configured DirectAccess, add the second consecutive public IPv4 address to the external network interface and then execute the following PowerShell command from an elevated command prompt.

Set-DAServer –TeredoState Enabled

Enable Teredo Support after DirectAccess Has Been Configured

Once complete, you’ll receive a warning message that states:

WARNING: Two consecutive IPv4 addresses have been detected on the Remote Access server, and Teredo is enabled. To use Teredo, ensure that internal servers allow inbound ICMP traffic.

Teredo requires that ICMPv4 Echo Requests be allowed inbound to any Intranet resource that a DirectAccess client will access. Ensure that all firewalls (host and network) are configured to allow ICMPv4 Echo Request inbound and outbound to ensure proper Teredo operation.

Once complete, close and then reopen the Remote Access Management console (in some cases a server restart may be required) to confirm Teredo support.

Enable Teredo Support after DirectAccess Has Been Configured

ISP Address Field is Blank in DirectAccess Status and Reports

When viewing DirectAccess client status in the Remote Access Management console, you will notice that the ISP address field is blank for clients using the IP-HTTPS IPv6 transition protocol. However, the ISP Address information is displayed for clients using the 6to4 or Teredo IPv6 transition protocols.

ISP Address Field is Blank in DirectAccess Status and Reports

This is expected behavior and occurs as a result of the way in which the DirectAccess reports obtain the client’s public ISP address information. The ISP address is derived from the IPv6 address used to establish the DirectAccess client’s IPsec Security Associations (SAs) on the DirectAccess server. For clients using the 6to4 or Teredo IPv6 transition protocols, the client’s public IPv4 address is embedded in its IPv6 address. This information is displayed in the ISP Address field. However, the IP-HTTPS IPv6 transition protocol uses completely random IPv6 addresses. Without an embedded IPv4 address, the Remote Access Management console lacks the information to display in the ISP Address field.

Updated 3/22/2015: With a little extra work it is possible to find the IPv4 ISP address for DirectAccess clients using the IP-HTTPS IPv6 transition protocol. For more information, please refer to Microsoft PFE Martin Solis’ excellent blog post on the subject here.

DirectAccess Load Balancing and Multisite Configuration Options Unavailable

Looking for more information about DirectAccess load balancing? See my post entitled DirectAccess Deployment Guide for Kemp LoadMaster Load Balancers.

DirectAccess in Windows Server 2012 R2 supports load balancing and multisite configuration options to provide both local and geographic redundancy, respectively. To configure either of these options, open the Remote Access Management console, expand Configuration in the navigation tree, highlight DirectAccess and VPN, and then select either Enable Multisite or Enable Load Balancing in the Tasks pane.

DirectAccess Load Balancing and Multisite Configuration Options Unavailable

Depending on your configuration you may encounter a scenario in which these features do not appear in the Remote Access Management console.

DirectAccess Load Balancing and Multisite Configuration Options Unavailable

This occurs when the Web Application Proxy (WAP) role is installed on the DirectAccess server. Although this is a supported configuration, enabling load balancing or multisite on a DirectAccess server with WAP installed requires additional configuration. Specifically, load balancing and/or multisite must be configured before installing the WAP role.

To restore support for load balancing and multisite configuration options, remove the WAP role using the GUI or with the Uninstall-WindowsFeature Web-Application-Proxy PowerShell command.

Disable 6to4 IPv6 Transition Protocol for DirectAccess Clients

Introduction

DirectAccess client to server connections are established exclusively over IPv6. To allow for this communication to take place over the public IPv4 Internet, DirectAccess uses IPv6 transition protocols – 6to4, Teredo, and IP-HTTPS – to tunnel IPv6 communication over IPv4. 6to4 is supported when the DirectAccess server is edge facing with a public IPv4 address assigned to its external network interface. Two consecutive public IPv4 addresses are required to support Teredo. IP-HTTPS is used in all scenarios, and exclusively when the DirectAccess server is located in a perimeter or DMZ network behind a NAT device.

6to4 and Teredo Advantages

Not all IPv6 transition protocols are created equal. For Windows 7 clients, 6to4 and Teredo provide significant performance advantages when compared to IP-HTTPS (Windows 8.x clients can use null encryption for IP-HTTPS, which eliminates this performance advantage). 6to4 and Teredo offer nearly identical performance, but 6to4 suffers from some unique challenges and should be disabled by default for all DirectAccess deployments.

Note: IP-HTTPS null encryption is disabled for all clients when client-based remote access VPN or one-time password (OTP) authentication is configured on the DirectAccess server, which can impact performance for Windows 8.x clients using IP-HTTPS.

Unreliable Fallback

The 6to4 IPv6 transition protocol is used when a DirectAccess client has a public IPv4 address assigned to its network interface. 6to4 uses IP protocol 41 for transport, and does not work when the client is behind a NAT. If outbound IP protocol 41 is blocked (a common scenario) then the client should fallback to Teredo or IP-HTTPS. In my experience this doesn’t always happen. In fact, the protocol fallback fails with enough regularity that it is the primary reason I recommend disabling it by default.

Active Directory IP Subnet Assignment

6to4 is also problematic when it comes to configuring Active Directory IP subnets for clients in a multisite DirectAccess deployment. 6to4 addresses begin with the 2002::/16 prefix followed by the IPv4 address of the client represented in hexadecimal using the form WWXX:YYZZ::WWXX:YYZZ. For example, if the DirectAccess client’s public IPv4 address is 198.51.100.83, its 6to4 address would be 2002:c633:6453::c633:6453. Since this IPv6 address is created using only the client’s IPv4 address, there is no way to associate the client to a specific entry point. The administrator is left with assigning the 2002::/16 prefix to the most centrally located AD site. This will undoubtedly result in some DirectAccess clients using domain controllers that are not ideal, which will ultimately lead to slow log on times and mapped drive failures.

Summary

In some deployment scenarios, 6to4 and Teredo offer performance advantages when compared to IP-HTTPS. Performance is identical for both 6to4 and Teredo, and considering the challenges that 6to4 poses, it should be disabled by default for DirectAccess deployments. This eliminates the possibility of associated connectivity issues, while still allowing DirectAccess clients to use the Teredo IPv6 transition protocol and not incur any performance penalty. Details about disabling IPv6 transition protocols can be found here.

Active Directory IP Subnets for DirectAccess Clients

Introduction

When deploying Windows Server 2012 R2 DirectAccess I’m often asked which Active Directory (AD) site a client is associated with when it establishes DirectAccess connectivity. The answer depends on the client’s operating system. Windows 8.x and later clients automatically associate themselves with the site to which the DirectAccess server they are connected to belongs. Windows 7 clients lack this capability, and depending on current AD configuration, Windows 7 clients may associate with an incorrect site. This can lead to potential problems such as slow logon times and mapped drive failures. To address this issue it is important to configure IP subnets in AD for DirectAccess clients to eliminate any potential problems. In this article I’ll demonstrate how to create IP subnets in AD and how to identify IPv6 subnets used by DirectAccess clients.

Active Directory IP Subnets

Configuring IP subnets in AD is relatively straightforward. In the Active Directory Sites and Services management console, right-click Subnets and choose New Subnet. Enter the IP subnet prefix and select the AD site where the DirectAccess server for this subnet resides.

Active Directory IP Subnets for DirectAccess Clients

IPv6 Subnets for DirectAccess Clients

To configure AD IP subnets for DirectAccess clients, it will be necessary to identify all potential IP subnets that may be in use. IP subnets used by DirectAccess clients depend on the IPv6 transition protocols supported by the DirectAccess configuration. DirectAccess supports 6to4, Teredo, and IP-HTTPS for client to server communication, and the Intrasite Automatic Tunnel Addressing Protocol (ISATAP) for manage-out connectivity. Any or all of these protocols may be used for a particular DirectAccess configuration.

  • 6to4 – Supported if the DirectAccess server is edge-facing with a public IPv4 address assigned to its external network interface.
  • Teredo – Supported if the DirectAccess server is edge-facing with two consecutive public IPv4 addresses assigned to its external network interface.
  • IP-HTTPS – Supported in all deployment scenarios, and is used exclusively if the DirectAccess server is located behind a NAT device in a perimeter or DMZ network.
  • ISATAP – Optionally used when manage out is enabled and configured.

IP subnets should be configured in AD for all IPv6 transition protocols supported for the DirectAccess deployment.

Identify the 6to4 IPv6 Subnet

Note: Information for the 6to4 protocol is provided here for completeness. However, it is generally recommended that 6to4 be disabled for DirectAccess deployments, making this configuration unnecessary. More information about disabling 6to4 can be found here.

The 6to4 IPv6 transition protocol is only supported when the DirectAccess server is edge-facing with a public IPv4 address assigned to its external network interface. 6to4 IPv6 addresses are assigned using the 2002::/16 prefix. For single site DirectAccess deployments, an administrator should create an IP subnet in AD using this prefix and assign it to the AD site where the DirectAccess server resides. If public IPv4 addressing is used internally and the 6to4 transition protocol has not been disabled, it is essential that more specific IP subnets for internal 6to4 clients also be configured.

6to4 and DirectAccess Multisite Challenges

The 6to4 IPv6 transition protocol presents a challenge for multisite DirectAccess deployments. When a client creates a 6to4 IPv6 address, it appends the 2002::/16 prefix with its public IPv4 address represented in hexadecimal using the form WWXX:YYZZ::WWXX:YYZZ. For example, if the DirectAccess client’s public IPv4 address is 198.51.100.83, its 6to4 address would be 2002:c633:6453::c633:6453. Since this IPv6 address is created using only the client’s IPv4 address, there is no way to associate the client to a specific entry point. This is one of the reasons why 6to4 is not recommended for use in DirectAccess deployments. If you must support the 6to4 IPv6 transition protocol in a multisite configuration, assign the 2002::/16 IP subnet to the most centrally located AD site.

Identify the Teredo IPv6 Subnet

The Teredo IPv6 transition protocol is only supported when the DirectAccess server is edge facing with two consecutive public IPv4 addresses assigned to its external network interface. Teredo IPv6 addresses begin with 2001: followed by the primary public IPv4 address (represented in hexadecimal) of the DirectAccess server. For example, if the DirectAccess server’s primary public IPv4 address is 203.0.113.240, the DirectAccess client will be assigned a Teredo IPv6 address using the 2001:cb00:71f0::/48 prefix. An administrator should create an IP subnet in AD using this prefix and assign it to the AD site where the DirectAccess server resides. For multisite deployments, repeat these steps for each DirectAccess entry point.

Identify the IP-HTTPS IPv6 Subnet

The IP-HTTPS IPv6 transition protocol is supported in all DirectAccess configurations and its IPv6 subnet should always be assigned to an AD site. The IP-HTTPS IPv6 prefix assignment differs between single site and multisite deployments.

Single Site Deployment

For single site deployments, a /64 IPv6 prefix is assigned for DirectAccess clients. To identify this subnet, run the Get-RemoteAccess PowerShell command on the DirectAccess server and locate the value of ClientIPv6Prefix

Active Directory IP Subnets for DirectAccess Clients

Multisite Deployment

For multisite deployments, a unique /64  IPv6 subnet is assigned to single node entry points. If load balancing is enabled, a /59 IPv6 subnet is assigned to the entry point, and each server within the entry point is assigned a /64 prefix for DirectAccess clients. To identify the IPv6 prefixes for each entry point, highlight DirectAccess and VPN below the Configuration node in the Remote Access Management console, and then select the DirectAccess entry point.

Active Directory IP Subnets for DirectAccess Clients

For edge facing deployments with a public IPv4 address assigned to the external network interface, the IPv6 prefix assigned to DirectAccess clients is from the 2002::/16 globally unique address (GUA) range. If the DirectAccess server is configured using a private IPv4 address with a single network interface or with two network interfaces behind a NAT, the IPv6 prefix assigned to DirectAccess clients will be from the fd00::/8 unique local address (ULA) range. An administrator should create an IP subnet in AD using this prefix and assign it to the AD site where the DirectAccess server resides.

Note: Uninstalling and reinstalling DirectAccess will result in a new IP-HTTPS network ID being created. If these changes are made, be sure to update AD IP subnets accordingly.

Identify the ISATAP IPv6 Subnet

Although this article focuses primarily on the IPv6 subnets used by remote DirectAccess clients, it is also important not to overlook AD IP subnet configuration for internal clients if ISATAP is configured for manage out. IP subnets used by ISATAP clients vary depending on the network configuration of the DirectAccess server.

Edge Deployment

For edge deployments, ISATAP addresses are assigned from the 2002::/16 GUA range. This is appended with the public IPv4 address of the DirectAccess server in hexadecimal using the form WWXX:YYZZ:1:0:5efe and the IPv4 address of the ISTAP client in familiar dotted-decimal notation. For example, if the DirectAccess server’s primary public IPv4 address is 203.0.113.240 and the client’s IP address is 172.16.1.77, the DirectAccess client will be assigned the ISATAP address 2002:cb00:71f0:1:0:5efe:172.16.1.77. The subnet to be created by the administrator in AD will then be 2002:cb00:71f0:1:0:5efe::/96 plus the IPv4 network prefix. For example, if the client’s IP address uses a /24 prefix, the AD IP subnet would be configured using 2002:cb00:71f0:1:0:5efe:172.16.1.0/120. This IP subnet should be assigned to the same site where the corresponding IPv4 subnet is assigned.

Perimeter/DMZ Deployment

For perimeter/DMZ deployments, ISATAP addresses are assigned randomly from the fd00::/8 ULA range and begin with fdXX:XXXX:XXXX:1:0:5efe followed by the IPv4 address of the ISTAP client in dotted-decimal notation. For example, if the DirectAccess client’s IP address is 172.16.1.77, its ISATAP address might look like fdca:3ce5:b0a:1:0:5efe:172.16.1.77. The subnet to be created by the administrator in AD will then be fdca:3ce5:b0a:1:0:5efe::/96 plus the IPv4 network prefix. If the clients’ IP address uses a /24 prefix, the AD IP subnet would be configured using fdca:3ce5:b0a:1:0:5efe:172.16.1.0/120. This IP subnet should be assigned to the same site where the corresponding IPv4 subnet is assigned.

Summary

The configuration of Active Directory IP subnets for DirectAccess clients is an often overlooked aspect of DirectAccess deployments. Proper IP subnet mapping to AD sites is critical, especially for large enterprise deployments with complex networks spanning multiple physical locations. It ensures that Windows 7 DirectAccess clients communicate with the closest AD domain controller when they establish a DirectAccess connection, which can eliminate potential issues. In addition, it is recommended to disable 6to4 for DirectAccess clients to avoid the pitfalls that come with the use of this IPv6 transition protocol. Also, don’t forget to configure IP subnets for any internal clients that use ISATAP for manage out.

Forwarding is Disabled on the DirectAccess Teredo Server

Recently while working with a customer to configure Windows Server 2012 R2 DirectAccess I encountered an issue with Teredo failing after enabling multisite. The remote access management console reported the following error:

Teredo: Not working properly
Error: Forwarding is disabled on the Teredo server.

Forwarding is Disabled on the DirectAccess Teredo Server

The resolution is simple enough. Enable forwarding on the Teredo interface! To do this we’ll need to identity the interface index of the Teredo Tunneling Pseudo-Interface and then enable forwarding using netsh.exe. Open an elevated command prompt and issue the following command:

netsh interface ipv6 show interface

Forwarding is Disabled on the DirectAccess Teredo Server

Make a note of the Teredo tunneling interface index and then enable forwarding on this interface by issuing the following command:

netsh interface ipv6 set interface  forwarding=enabled

Forwarding is Disabled on the DirectAccess Teredo Server

DirectAccess IPv6 Transition Protocols Explained

Introduction

From a client perspective, DirectAccess is an IPv6-only solution. The DirectAccess client communicates with the DirectAccess server exclusively using IPv6. However, IPv6 is not widely deployed, so the most common scenario will find your DirectAccess clients and servers on the IPv4 Internet.

To facilitate DirectAccess client to server communication with IPv6 when the client is on the IPv4 Internet, IPv6 transition protocols are employed. These protocols effectively tunnel IPv6 packets in IPv4 packets. DirectAccess makes use of three IPv6 transition protocols for client to server connections – 6to4, Teredo, and IP-HTTPS.

DirectAccess Transition Protocols

6to4 – The 6to4 IPv6 transition protocol works by encapsulating IPv6 packets in IPv4 packets using IP protocol 41. 6to4 does not work when the client or the server is behind a NAT, so this IPv6 transition protocol is only used when the client and server are assigned public IPv4 addresses. DirectAccess clients with public IPv4 addresses aren’t common though, and there are some challenges with the stability of 6to4. From experience I can tell you that 6to4 often fails when clients use a cellular Wi-Fi hotspot, for example. For this reason it is generally recommended that you proactively disable this transition protocol to avoid potential issues in the future.

TeredoTeredo is an IPv6 transition protocol that is designed to work when a DirectAccess client (but not the DirectAccess server) is behind a NAT. It works by encapsulating IPv6 packets in IPv4 packets using UDP on port 3544. Teredo will be used any time the DirectAccess client has a private IPv4 address, or when the client has a public IPv4 address and the 6to4 protocol is unavailable (e.g. 6to4 is disabled, or outbound access to IP protocol 41 is restricted by firewall policy). To support Teredo, the DirectAccess server must be configured with two consecutive public IPv4 addresses. In addition, Teredo uses ICMP for NAT detection (e.g. cone, restricted, symmetric), so ICMPv4 echo requests must be allowed inbound to any host with which the DirectAccess client communicates.

IP-HTTPSIP-HTTPS is an IPv6 transition protocol that works by encapsulating IPv6 packets in IPv4 packets using HTTP with SSL/TLS. It is the IPv6 transition protocol of last resort, and will be used any time that 6to4 or Teredo aren’t available. The advantage to using IP-HTTPS is ubiquitous firewall access. Any network with access to the public Internet should, at a minimum, allow outbound HTTP and HTTPS. In some deployment scenarios, IP-HTTPS can be disadvantageous. For example, when Windows 7 DirectAccess clients leverage this IPv6 transition protocol, IPsec-encrypted traffic is encrypted again using SSL/TLS. This double encryption results in high processing overhead and often translates to poor performance and limited scalability. Windows 8 and later clients do not suffer this limitation, as they support null encryption which eliminates the negative effects imposed by double encryption. For the best results using IP-HTTPS, use an application delivery controller to offload SSL, or deploy Windows 8 or later clients. In any case, do not collocate the client-based VPN role on the DirectAccess server, as doing so will remove support for null encryption completely and force even Windows 8 and later clients to perform double encryption for IP-HTTPS traffic.

DirectAccess Server Configuration

To support the 6to4 and Teredo IPv6 transition protocols, the DirectAccess server must be configured with two network interfaces; one internal and one external. The DirectAccess server must have public IPv4 addresses assigned to its external network interface. For Teredo in particular, the DirectAccess server requires two consecutive public IPv4 addresses. Beginning with Windows Server 2012, DirectAccess provides support for DMZ/perimeter network deployment behind a NAT device using RFC1918 private IPv4 addresses with either one or two network interfaces. In this deployment scenario, the DirectAccess server only supports the use of the IP-HTTPS IPv6 transition protocol. 6to4 and Teredo are not available when the DirectAccess server is located behind a NAT device and these IPv6 transition protocols should be disabled on all DirectAccess clients.

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