DirectAccess NRPT Configuration with Split DNS

DirectAccess NRPT Configuration with Split DNSThe Name Resolution Policy Table (NRPT) in Windows provides policy-based name resolution request routing for DNS queries. DirectAccess uses the NRPT to ensure that only requests for resources in the internal namespace, as defined by the DirectAccess administrator, are sent over the DirectAccess connection. DNS queries for all other namespaces are sent to the DNS servers defined on the client’s network interface.

Note: This behavior changes when force tunneling is enabled. In this case, all DNS queries are sent over the DirectAccess connection with the exception of the NLS and the DirectAccess server’s public hostname(s). If force tunneling is enabled, the configuration guidance described below is not required.

Split DNS

NRPT configuration is straightforward when the internal and external namespaces are unique. However, when split DNS is used, meaning when the internal and external namespaces are the same, DirectAccess configuration is more challenging. Typically, there may be many resources that should not go over the DirectAccess connection, such as public-facing web servers, email and unified communications servers, federation servers, etc. Without additional configuration, requests for all of these services would go over the DirectAccess connection. That may or may not be desirable, depending on the requirements of the implementation.

DirectAccess Server

One crucial public resource is the DirectAccess server itself. When using split DNS, the DirectAccess implementation’s public hostname will, by default, be included in the internal namespace. In this scenario, the DirectAccess client will fail to establish a connection to the DirectAccess server.

Troubleshooting

When troubleshooting failed connectivity, the output of ipconfig will show the IP-HTTPS tunnel interface media state as “Media disconnected”.

DirectAccess NRPT Configuration with Split DNS

The output of Get-NetIPHttpsState will also return an error code 0x2AF9 with an interface status “Failed to connect to the IPHTTPS server; waiting to reconnect”.

DirectAccess NRPT Configuration with Split DNS

To further troubleshoot this issue, examine the output of Get-NetIPHttpsConfiguration. Test name resolution of the FQDN listed in the ServerURL field. If the issue is related to NRPT configuration, the client will fail to resolve this name to an IP address. Testing from a non-DirectAccess client should resolve correctly, however.

DirectAccess NRPT Configuration with Split DNS

NRPT Configuration

If split DNS is employed, it is necessary to include the DirectAccess server’s public hostname in the NRPT as an exemption. This will cause the DNS query for the public hostname to use public DNS servers, allowing the DirectAccess client to establish a connection successfully.

To resolve this issue, open the Remote Access Management console on the DirectAccess server, highlight DirectAccess and VPN under Configuration, and then click Edit on Step 3. Select DNS, and then double-click on an empty row in the table.

DirectAccess NRPT Configuration with Split DNS

Enter the public hostname for the DirectAccess deployment in the DNS suffix field (the public hostname can be found by clicking Edit on Step 2). Do NOT specify a DNS server. Click Apply, click Next twice, and then click Finish.

DirectAccess NRPT Configuration with Split DNS

Note: For multisite deployments, be sure to include the public hostname for each entry point in the enterprise. Also, if multisite is configured to use GSLB, include the GSLB hostname as well.

PowerShell

Alternatively, you can run the following PowerShell commands to automatically configure the NRPT for split DNS. For multisite deployments, be sure to run these commands on at least one DirectAccess server in each site.

$hostname = Get-RemoteAccess | Select-Object -ExpandProperty ConnectToAddress
Add-DAClientDnsConfiguration -DnsSuffix $hostname -PassThru

If multisite is configured to use GSLB, run the following PowerShell commands on one DirectAccess server in the enterprise.

$gslbfqdn = Get-DAMultiSite | Select-Object -ExpandProperty GslbFqdn
Add-DAClientDnsConfiguration -DnsSuffix $gslbfqdn -PassThru

Additional Information

Troubleshooting DirectAccess IP-HTTPS Error 0x2af9

DirectAccess DNS Not Working Properly

DirectAccess DNS Records Explained

Troubleshooting Name Resolution Issue on DirectAccess Clients

DirectAccess IP-HTTPS Null Cipher Suites Not Available

DirectAccess IP-HTTPS Null Cipher Suites Not AvailableMicrosoft first introduced support for null cipher suites for the IP-HTTPS IPv6 transition technology in Windows Server 2012, and it is supported for DirectAccess in Windows 8.x and Windows 10 clients. Using null cipher suites for IP-HTTPS eliminates the needless double encryption that occurs when using encrypted cipher suites. DirectAccess is a unique workload where SSL/TLS encryption isn’t really required because the payload being transported in HTTPS is already encrypted.

No Encryption by Design

When supporting Windows 8.x and Windows 10 clients, ensuring null cipher suites (TLS_RSA_WITH_NULL_SHA and TLS_RSA_WITH_NULL_SHA256) are enabled and operational is crucial to providing the highest levels of performance and scalability for the remote access solution. When following implementation best practices, this isn’t really an issue. However, in some cases null cipher suites may be disabled. This will result in reduced scalability and degraded performance for Windows 8.x and Windows 10 clients.

Validating SSL/TLS Configuration

The easiest way to verify that null cipher suites are being offered by the DirectAccess server is to use the Qualys SSL Labs server test site. Ideally you should see a result similar to this.

DirectAccess IP-HTTPS Null Cipher Suites Not AvailableFigure 1. Qualys SSL Labs server test site results for properly configured DirectAccess server.

Don’t be alarmed by the overall rating “F”. That happens because the Qualys test site is designed to test web servers where using null cipher suites would be a serious security issue. As I stated previously, the DirectAccess workload is unique in that its HTTPS payload is already encrypted, so using null cipher suites is acceptable in this scenario.

DirectAccess IP-HTTPS Null Cipher Suites Not AvailableFigure 2. Qualys SSL Labs server test site results for properly configured DirectAccess server showing support for null SSL/TLS cipher suites.

Null Cipher Suites Missing

When performing the Qualys SSL labs server test on a DirectAccess server, an overall rating of “A” is not desirable and indicates the DirectAccess server is misconfigured. This is caused by the lack of support for null cipher suites.

DirectAccess IP-HTTPS Null Cipher Suites Not AvailableFigure 3. Qualys SSL Labs server test site results for misconfigured DirectAccess server.

Common Causes

Null cipher suites for SSL and TLS can be disabled for a variety of reasons. Below are some of the most common causes for the lack of support for null cipher suites for DirectAccess.

Self-Signed Certificates – Using the Getting Started Wizard (simplified deployment) will configure DirectAccess using a self-signed certificate for IP-HTTPS. Using a self-signed certificate is discouraged for numerous reasons, most importantly because it disables support for null cipher suites.

Security Hardening – Security administrators may proactively disable support for null cipher suites in a misguided effort to “improve security” for DirectAccess. While this is acceptable and recommended on a web server, it is not advisable to disable null cipher suites on a DirectAccess server.

SSL Certificate Signing Algorithm – Using an SSL certificate signed with an Elliptical Curve (EC) key as opposed to an RSA key will result in the loss of support for null cipher suites for IP-HTTPS. High security/assurance certificates signed with EC keys are not recommended for use on DirectAccess servers and should be avoided if possible.

DirectAccess Configuration Options – Enabling One-Time Password (OTP) authentication on the DirectAccess server will also result in a loss of support for null cipher suites. Also, adding additional roles to the DirectAccess server such as client-based VPN or the Web Application Proxy (WAP) can also result in null cipher suites being disabled.

Summary

Null cipher suites are implemented by design on DirectAccess servers to enhance performance for Windows 8.x and Windows 10 clients and improve overall scalability for the implementation. They eliminate the pointless double encryption of DirectAccess communication, which itself is already encrypted. For optimal performance and scalability, be sure to follow implementation best practices and use a PKI-managed (public or private) SSL certificate signed with an RSA key (SHA-256 recommended). Resist the urge to “harden” the DirectAccess server by disabling support for null cipher suites, and avoid the use of SSL certificates signed with EC keys. In addition, carefully consider DirectAccess deployment options such as OTP authentication and consider deploying roles such as VPN and WAP on a separate server.

Additional Information

DirectAccess IP-HTTPS SSL and TLS Insecure Cipher Suites

DirectAccess IP-HTTPS Null Encryption and SSTP VPN

DirectAccess and FIPS Compliant Algorithms for Encryption

SSL Certificate Considerations for DirectAccess IP-HTTPS 

 

 

DirectAccess and FIPS Compliant Algorithms for Encryption

DirectAccess administrators may be required to enable Federal Information Processing Standards (FIPS) compliant algorithms for encryption, hashing, and signing on DirectAccess servers to meet certain regulatory and compliance requirements.

DirectAccess and FIPS Compliant Algorithms for Encryption

Performance Impact

Be advised that enabling this setting will disable support for null cipher suites for the IP-HTTPS IPv6 transition technology. This will result in the double encryption of all DirectAccess client communication, which will increase resource consumption on DirectAccess servers. This leads to reduced scalability and degraded performance for all DirectAccess clients, including Windows 8.x and Windows 10.

If enabling FIPS compliant cannot be avoided, additional compute capacity (CPU and memory) should be provisioned. For best results, add additional servers to distribute the workload and improve performance for DirectAccess clients.

Always On VPN

If you’re looking for better security and performance, consider migrating to Windows 10 Always On VPN. Always On VPN fully supports FIPS compliant algorithms without the negative performance impact associated with DirectAccess. If you’d like to learn more about security and Always On VPN, fill out the form below and I’ll get in touch with you.

Additional Resources

Always On VPN and the Future of DirectAccess 

5 Things DirectAccess Administrators Should Know About Always On VPN 

3 Important Advantages of Always On VPN over DirectAccess 

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!

SSL Certificate Considerations for DirectAccess IP-HTTPS

SSL Certificate Considerations for DirectAccess IP-HTTPSDirectAccess uses IPv6 exclusively for communication between the client and server. IPv6 transition technologies are used to support DirectAccess communication over the IPv4 public Internet. One of those IPv6 transition technologies, IP-HTTPS, uses HTTP for encapsulation and SSL/TLS for authentication of the DirectAccess server.

SSL Certificates

When configuring DirectAccess, an SSL certificate must be provided for IP-HTTPS. There are three different types of SSL certificates that can be used.

Public SSL Certificate – Using an SSL certificate signed by a public certification authority (CA) is the recommended best practice for configuring DirectAccess IP-HTTPS. This provides the highest level of assurance for DirectAccess clients connecting via IP-HTTPS.

Private SSL Certificate – Using an SSL certificate issued by the organization’s internal CA is an acceptable alternative to using a public SSL certificate in most cases. This can reduce the cost associated with obtaining the certificate, especially for multisite deployments.

Self-Signed Certificate – Using a self-signed certificate is not recommended and should be avoided in most deployment scenarios. A self-signed certificate provides no real assurance for DirectAccess clients. Crucially, using a self-signed certificate will disable support for null SSL and TLS cipher suites. This reduces the overall scalability and performance of the remote access solution.

SSL Certificate Considerations for DirectAccess IP-HTTPS

Figure 1. Null cipher suites not supported when using a self-signed SSL certificate for IP-HTTPS.

Certificate Requirements

The SSL certificate must include the Server Authentication (1.3.6.1.5.5.7.3.1) Enhanced Key Usage (EKU) Object Identifier (OID). It should use an RSA key of 2048 bits and be signed with SHA256. Using stronger keys provides no additional protection and should not be used. In addition, SSL certificates using ECDSA keys is not recommended, as they do not support null cipher suites.

Summary

In most cases, using a public SSL certificate is ideal. However, issuing a certificate from a private CA is also acceptable. Using self-signed certificates can be used for non-production testing and in very small production deployments, but should generally be avoided.

Additional Resources

DirectAccess IP-HTTPS SSL and TLS Insecure Cipher Suites

DirectAccess and Multi-SAN SSL Certificates for IP-HTTPS

Top 5 DirectAccess Troubleshooting PowerShell Commands

Top 5 DirectAccess Troubleshooting PowerShell CommandsNative PowerShell commands in Windows 10 make DirectAccess troubleshooting much easier than older operating systems like Windows 7. For example, with one PowerShell command an administrator can quickly determine if a DirectAccess client has received the DirectAccess client settings policy. In addition, PowerShell can be used to view the status of the connection and retrieve additional information or error codes that can be helpful for determining the cause of a failed connection. Further, PowerShell can also be used to review configuration details and perform other troubleshooting and connectivity validation tasks.

Here are my top 5 PowerShell commands for troubleshooting DirectAccess on Windows 10.

1. Get-DAClientExperienceConfiguration

Ensuring that the DirectAccess Client Settings group policy has been applied to the client is one of the first steps in troubleshooting failed DirectAccess connections. While it is possible to use gpresult to do this, using the Get-DAClientExperienceConfiguration PowerShell command is much simpler. If DirectAccess client settings have been applied, the output of the command will include information such as the IPsec tunnel endpoint IPv6 addresses and the Network Connectivity Assistant (NCA) corporate resource URL. If DirectAccess client settings have not been applied, this information will be missing.

Top 5 DirectAccess Troubleshooting PowerShell Commands

Figure 1. DirectAccess Client Settings group policy successfully applied.

Top 5 DirectAccess Troubleshooting PowerShell Commands

Figure 2. DirectAccess Client Settings group policy not applied.

2. Get-NetIPHttpsState

Performance improvements first introduced in Windows 8 have made IP-HTTPS the IPv6 transition technology of choice when it comes to supporting DirectAccess client connectivity. Also, if the DirectAccess server is located behind an edge device performing Network Address Translation (NAT), IP-HTTPS is the only supported transition technology. Using the Get-NetIPHttpsState PowerShell command, the DirectAccess administrator can quickly determine if the IP-HTTPS connection was successful. If it was not, the command will return an error code and interface status that will indicate why the IP-HTTPS connection was unsuccessful.

Top 5 DirectAccess Troubleshooting PowerShell Commands

Figure 3. Get-NetIPHttpsState

3. Get-NetIPHttpsConfiguration

When troubleshooting IP-HTTPS connection failures, it is necessary to obtain additional information to continue the troubleshooting process. Using the Get-NetIPHttpsConfiguration PowerShell command, the DirectAccess administrator can obtain the public hostname for the DirectAccess server and ensure that the name resolves to the correct IP address in DNS and that it is reachable on TCP port 443.

Top 5 DirectAccess Troubleshooting PowerShell Commands

Figure 4. Get-NetIPHttpsConfiguration

4. Resolve-DnsName

Using the Resolve-DnsName PowerShell command is crucial when performing any name resolution tasks on the DirectAccess client. This is because Resolve-DnsName is aware of the Name Resolution Policy Table (NRPT) and will direct name resolution requests accordingly. Tools like nslookup are DNS server testing tools and are unaware of the NRPT. Typically they do not yield expected results when testing name resolution on a DirectAccess client.

Top 5 DirectAccess Troubleshooting PowerShell Commands

Figure 5. Name resolution results from Resolve-DnsName and nslookup.

5. Get-DnsClientNrptPolicy

Often the cause of DirectAccess client connectivity issues is a misconfigured NRPT. Using the Get-DnsClientNrptPolicy PowerShell command the DirectAccess administrator can validate that name resolution requests for host names in any internal namespaces are being sent to the DirectAccess DNS64 IPv6 address.

Top 5 DirectAccess Troubleshooting PowerShell Commands

Figure 6. Get-DnsClientNrptPolicy

Additional Resources

Top 5 DirectAccess Troubleshooting Tips

Troubleshooting Name Resolution Issues on DirectAccess Clients

Learn PowerShell in a Month of Lunches Book by Don Jones and Jeff Hicks

Implementing DirectAccess with Windows Server 2016 Book

Planning and Implementing DirectAccess with Windows Server 2016 Video Training Course

Managing and Supporting DirectAccess with Windows Server 2016 Video Training Course

 

 

DirectAccess Reporting Fails and Schannel Event ID 36871 after Disabling TLS 1.0

IMPORTANT NOTE: The guidance in this post will disable support for null SSL/TLS cipher suites on the DirectAccess server. This will result in reduced scalability and performance for all clients, including Windows 8.x and Windows 10. It is recommended that TLS 1.0 not be disabled on the DirectAccess server if at all possible.

When performing security hardening on the DirectAccess server it is not uncommon to disable weak cipher suites or insecure protocols such as SSL 3.0 and TLS 1.0. However, after disabling SSL 3.0 and TLS 1.0 you will find that it is no longer possible generate reports. Clicking the Generate Report link in the Remote Access Management console returns no data.

DirectAccess Reporting Fails after Disabling TLS 1.0

In addition, the System event log indicates Schannel errors with Event ID 36871. The error message states that “A fatal error occurred while creating a TLS client credential. The internal error state is 10013.”

DirectAccess Reporting Fails after Disabling TLS 1.0

To resolve this issue and restore DirectAccess reporting functionality you must enable the use of FIPS compliant encryption algorithms on the DirectAccess server. This change can be made locally or via Active Directory group policy. Open the Group Policy Management Console (gpmc.msc) for Active Directory GPO, or the Local Group Policy Editor (gpedit.msc) on the DirectAccess server and navigate to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. Double-click System cryptography: Use FIPS compliant algorithms for encryption, hashing, and signing and select Enabled.

DirectAccess Reporting Fails after Disabling TLS 1.0

If using Active Directory GPO, ensure that the GPO is applied all DirectAccess servers in the organization. A restart is not required for this setting to take effect. Once this change has been made, reporting should work as expected.

Additional Resources

DirectAccess IP-HTTPS SSL and TLS Insecure Cipher Suites
DirectAccess Video Training Courses on Pluralsight
Implementing DirectAccess with Windows Server 2016 Book on Amazon.com

DirectAccess Manage Out and System Center Configuration Manager (SCCM)

The seamless and transparent nature of DirectAccess makes it wonderfully easy to use. In most cases, it requires no user interaction at all to access internal corporate resources while away from the office. This enables users to be more productive. At the same time, it offers important connectivity benefits for IT administrators and systems management engineers as well.

Always Managed

DirectAccess Manage Out and System Center Configuration Manager (SCCM)DirectAccess clients are automatically connected to the corporate network any time they have a working Internet connection. Having consistent corporate network connectivity means they receive Active Directory group policy updates on a regular basis, just as on-premises systems do. Importantly, they check in with internal management systems such as System Center Configuration Manager (SCCM) and Windows Server Update Services (WSUS) servers, enabling them to receive updates in a timely manner. Thus, DirectAccess clients are better managed, allowing administrators to more effectively maintain the configuration state and security posture for all their managed systems, including those that are predominantly field-based. This is especially crucial considering the prevalence WannaCry, Cryptolocker, and a variety of other types of ransomware.

DirectAccess Manage Out

DirectAccess Manage Out and System Center Configuration Manager (SCCM)When manage out is configured with DirectAccess, hosts on the internal network can initiate connections outbound to remote connected DirectAccess clients. SCCM Remote Control and Remote Desktop Connection (RDC) are commonly used to remotely connect to systems for troubleshooting and support. With DirectAccess manage out enabled, these and other popular administrative tools such as VNC, Windows Remote Assistance, and PowerShell remoting can also be used to manage remote DirectAccess clients in the field. In addition, enabling manage out allows for the proactive installation of agents and other software on remote clients, such as the SCCM and System Center Operation Manager (SCOM) agents, third-party management agents, antivirus and antimalware software, and more. A user does not have to be logged on to their machine for manage out to work.

IPv6

DirectAccess manage out requires that connections initiated by machines on the internal network to remote-connected DirectAccess clients must be made using IPv6. This is because DirectAccess clients use IPv6 exclusively to connect to the DirectAccess server. To enable connectivity over the public IPv4 Internet, clients use IPv6 transition technologies (6to4, Teredo, IP-HTTPS), and IPv6 translation components on the server (DNS64 and NAT64) enable clients to communicate with internal IPv4 resources. However, DNS64 and NAT64 only translate IPv6 to IPv4 inbound. They do not work in reverse.

Native or Transition?

It is recommended that IPv6 be deployed on the internal network to enable DirectAccess manage out. This is not a trivial task, and many organizations can’t justify the deployment for just this one specific use case. As an alternative, IPv6 can be configured with an IPv6 transition technology, specifically the Intrasite Automatic Tunnel Addressing Protocol (ISATAP). ISATAP functions as an IPv6 overlay network, allowing internal hosts to obtain IPv6 addresses and routing information from an ISATAP router to support manage out for DirectAccess clients.

ISATAP

When DirectAccess is installed, the server is automatically configured as an ISATAP router. Guidance for configuring ISATAP clients can be found here. Using ISATAP can be an effective approach to enabling DirectAccess manage out for SCCM when native IPv6 is not available, but it is not without its drawbacks.

• Using the DirectAccess server for ISATAP is only supported with single server DirectAccess deployments.
• Using the DirectAccess server for ISATAP does work when using Network Load Balancing (NLB) with some additional configuration, but it is not supported.
• Using the DirectAccess server for ISATAP does not work when an external load balancer is used, or if multisite is enabled.

ISATAP with Load Balancing and Multisite

It is technically possible to enable DirectAccess manage out for SCCM using ISATAP in load-balanced and multisite DirectAccess deployments, however. It involves deploying a separate ISATAP router and some custom configuration, but once in place it works perfectly. I offer this service to my customers as part of a consulting engagement. If you’re interested in restoring DirectAccess manage out functionality to support SCCM remote control, RDC, or VNC in load-balanced or multisite DirectAccess deployments, fill out the form below and I’ll provide you with more information.

Additional Resources

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
Video: Windows 10 DirectAccess in action (includes manage out demonstration)

Deployment Considerations for DirectAccess on Amazon Web Services (AWS)

Organizations are rapidly deploying Windows server infrastructure with public cloud providers such as Amazon Web Services (AWS) and Microsoft Azure. With traditional on-premises infrastructure now hosted in the cloud, DirectAccess is also being deployed there more commonly.

Supportability

Interestingly, Microsoft has expressly stated that DirectAccess is not formally supported on their own public cloud platform, Azure. However, there is no formal statement of non-support for DirectAccess hosted on other non-Microsoft public cloud platforms. With supportability for DirectAccess on AWS unclear, many companies are taking the approach that if it isn’t unsupported, then it must be supported. I’d suggest proceeding with caution, as Microsoft could issue formal guidance to the contrary in the future.

DirectAccess on AWS

Deploying DirectAccess on AWS is similar to deploying on premises, with a few notable exceptions, outlined below.

IP Addressing

It is recommended that an IP address be exclusively assigned to the DirectAccess server in AWS, as shown here.

Deployment Considerations for DirectAccess on Amazon Web Services (AWS)

Prerequisites Check

When first configuring DirectAccess, the administrator will encounter the following warning message.

“The server does not comply with some DirectAccess prerequisites. Resolve all issues before proceed with DirectAccess deployment.”

The warning message itself states that “One or more network adapters should be configured with a static IP address. Obtain a static address and assign it to the adapter.

Deployment Considerations for DirectAccess on Amazon Web Services (AWS)

IP addressing for virtual machines are managed entirely by AWS. This means the DirectAccess server will have a DHCP-assigned address, even when an IP address is specified in AWS. Assigning static IP addresses in the guest virtual machine itself is also not supported. However, this warning message can safely be ignored.

No Support for Load Balancing

It is not possible to create load-balanced clusters of DirectAccess servers for redundancy or scalability on AWS. This is because enabling load balancing for DirectAccess requires the IP address of the DirectAccess server be changed in the operating system, which is not supported on AWS. To eliminate single points of failure in the DirectAccess architecture or to add additional capacity, multisite must be enabled. Each additional DirectAccess server must be provisioned as an individual entry point.

Network Topology

DirectAccess servers on AWS can be provisioned with one or two network interfaces. Using two network interfaces is recommended, with the external network interface of the DirectAccess server residing in a dedicated perimeter/DMZ network. The external network interface must use either the Public or Private Windows firewall profile. DirectAccess will not work if the external interface uses the Domain profile. For the Public and Private profile to be enabled, domain controllers must not be reachable from the perimeter/DMZ network. Ensure the perimeter/DMZ network cannot access the internal network by restricting network access in EC2 using a Security Group, or on the VPC using a Network Access Control List (ACL) or custom route table settings.

External Connectivity

A public IPv4 address must be associated with the DirectAccess server in AWS. There are several ways to accomplish this. The simplest way is to assign a public IPv4 address to the virtual machine (VM). However, a public IP address can only be assigned to the VM when it is deployed initially and cannot be added later. Alternatively, an Elastic IP can be provisioned and assigned to the DirectAccess server at any time.

An ACL must also be configured for the public IP that restricts access from the Internet to only inbound TCP port 443. To provide additional protection, consider deploying an Application Delivery Controller (ADC) appliance like the Citrix NetScaler or F5 BIG-IP to enforce client certificate authentication for DirectAccess clients.

Network Location Server (NLS)

If an organization is hosting all of its Windows infrastructure in AWS and all clients will be remote, Network Location Server (NLS) availability becomes much less critical than with traditional on-premises deployments. For cloud-only deployments, hosting the NLS on the DirectAccess server is a viable option. It eliminates the need for dedicated NLS, reducing costs and administrative overhead. If multisite is configured, ensure that the NLS is not using a self-signed certificate, as this is unsupported.

Deployment Considerations for DirectAccess on Amazon Web Services (AWS)

However, for hybrid cloud deployments where on-premises DirectAccess clients share the same internal network with cloud-hosted DirectAccess servers, it is recommended that the NLS be deployed on dedicated, highly available servers following the guidance outlined here and here.

Client Provisioning

All supported DirectAccess clients will work with DirectAccess on AWS. If the domain infrastructure is hosted exclusively in AWS, provisioning clients can be performed using Offline Domain Join (ODJ). Provisioning DirectAccess clients using ODJ is only supported in Windows 8.x/10. Windows 7 clients cannot be provisioned using ODJ and must be joined to the domain using another form of remote network connectivity such as VPN.

Additional Resources

DirectAccess No Longer Supported in Microsoft Azure

Microsoft Server Software Support for Azure Virtual Machines

DirectAccess Network Location Server (NLS) Guidance

DirectAccess Network Location Server (NLS) Deployment Considerations for Large Enterprises

Provisioning DirectAccess Clients using Offline Domain Join (ODJ)

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

DirectAccess SSL Offload and IP-HTTPS Preauthentication with F5 BIG-IP

Planning and Implementing DirectAccess with Windows Server 2016 Video Training Course

Implementing DirectAccess with Windows Server 2016 Book

DirectAccess Troubleshooting with Nmap

DirectAccess IP-HTTPS Discovery Script for NmapDirectAccess troubleshooting can be made much easier using open source tools such as Nmap. Nmap can be used to perform many essential network connectivity and configuration checks, including validating network paths, confirming DirectAccess server response, and viewing SSL configuration. Nmap can also be used to ensure that the attack surface of the DirectAccess server is properly minimized. Some tests can be performed using only native Nmap functionality, while others require the use of specialized Nmap scripts that are included with the tool.

Installation

Nmap can be installed on a wide variety of operating systems, including Windows. If you plan to install Nmap on Windows, be sure to also install WinPcap and the Microsoft Visual C++ 2013 Redistributable. The Visual C++ component is included with the Nmap download. WinPcap must be downloaded separately here.

Testing External Connectivity

Validating external connectivity is often one of the first DirectAccess troubleshooting steps I take. Confirm that the DirectAccess public hostname resolves to the correct IP address, then run the following Nmap command to validate network connectivity from the Internet to the DirectAccess server.

nmap -n -Pn -p443 <da_public_hostname>

DirectAccess Troubleshooting with Nmap

If the hostname resolves correctly and the network path is complete, the server should respond and Nmap will show the port as open. However, this doesn’t necessarily mean that the DirectAccess server is the device that replied! Due to misconfiguration, it is possible that another server or network device listening on TCP port 443 responded, so this is not a conclusive test.

DirectAccess Server Response

To confirm the DirectAccess server is responding to HTTPS requests and not some other server or device, run the following Nmap command with the ip-https-discover script.

nmap -n -Pn -p443 <da_public_hostname> –script ip-https-discover

If the DirectAccess server responds to the request, Nmap will return the following message:

IP-HTTPS is supported. This indicates that this host supports Microsoft DirectAccess.

DirectAccess Troubleshooting with Nmap

If the port is open but the script does not return this message, it is likely that another server or device is responding on TCP port 443, not the DirectAccess server.

Note: If an Application Delivery Controller (ADC) is configured to perform IP-HTTPS preauthentication, the Nmap IP-HTTPS discovery script will not return this result. This is expected and by design.

SSL Certificate Validation

It is not uncommon for DirectAccess clients to fail to connect via IP-HTTPS because of SSL certificate issues. Specifically, an SSL certificate that is not trusted, is expired, or its subject field does not match the public hostname will prevent DirectAccess clients from connecting. To view the SSL certificate configuration of a DirectAccess server, run the following Nmap command with the ssl-cert script.

nmap -n -Pn -p443 <da_public_hostname> –script ssl-cert

DirectAccess Troubleshooting with Nmap

SSL Cipher Suite Configuration

Occasionally there can be issues with the SSL configuration on the DirectAccess server that prevent some clients from connecting, or result in poor performance. This commonly occurs when administrators perform SSL hardening on the DirectAccess server and remove support for null cipher suites. Null cipher suites should never be disabled on the DirectAccess server. They are important to ensure the highest levels of performance for Windows 8.x and Windows 10 clients. Also, if an Application Delivery Controller (ADC) or load balancer is performing SSL offload, lack of support for null cipher suites will prevent Windows 8.x and Windows 10 clients from connecting. To determine if the DirectAccess server supports null cipher suites, run the following Nmap command with the ssl-enum-ciphers script.

nmap -n -Pn -p443 <da_public_hostname> –script ssl-enum-ciphers

DirectAccess Troubleshooting with Nmap

Attack Surface Audit

If DirectAccess implementation and security best practices are followed, the DirectAccess server will be behind an edge firewall. The only port required to be allowed inbound for DirectAccess is TCP port 443. It is recommended that a full port scan be performed against the DirectAccess server’s public IPv4 address to identify any unnecessary ports that may be open externally. To perform a full port scan, run the following Nmap command.

nmap -n -Pn -p- <da_public_hostname>

Ideally it should look like this.

DirectAccess Troubleshooting with Nmap

If it looks something like this, you’re in serious trouble!

DirectAccess Troubleshooting with Nmap

The DirectAccess server should never be listening for requests other that HTTPS on the public Internet. Exposing services such as SMB (TCP port 445), RDP (TCP port 3389), and others presents a significant security risk. It is recommended that edge firewalls be configured to allow inbound TCP port 443 only. If the DirectAccess server is connected directly to the public Internet (not recommended!) then the Windows Firewall should be configured to restrict access to inbound TCP port 443 only.

Additional Resources

DirectAccess IP-HTTPS Discovery Script for Nmap
Planning and Implementing DirectAccess with Windows Server 2016 on Pluralsight
Implementing DirectAccess with Windows Server 2016 Book
DirectAccess Troubleshooting and Consulting Services

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