Troubleshooting DirectAccess IP-HTTPS Error 0x80090326

A Windows 7 or Windows 8.x/10 client may fail to establish a DirectAccess connection using the IP-HTTPS IPv6 transition technology. When troubleshooting this issue, running ipconfig.exe shows that the media state for the tunnel adapter iphttpsinterface is Media disconnected.

Troubleshooting DirectAccess IP-HTTPS Error 0x80090326

Running the Get-NetIPHttpsState PowerShell command on Windows 8.x/10 clients or the netsh interface httpstunnel show interface command on Windows 7 clients returns and error code of 0x80090326, with an interface status Failed to connect to the IPHTTPS server; waiting to reconnect.

Troubleshooting DirectAccess IP-HTTPS Error 0x80090326

Error code 0x80090326 translates to SEC_E_ILLEGAL_MESSAGE, indicating the client encountered a fatal error during the SSL handshake.

Troubleshooting DirectAccess IP-HTTPS Error 0x80090326

There are a number of things that can cause this to happen. The most common scenario occurs when an Application Delivery Controller (ADC) is improperly configured to perform client certificate authentication for IP-HTTPS connections. Common examples are an incorrect or missing root CA certificate, or null SSL/TLS cipher suites not enabled when supporting Windows 8.x/10 clients.

To troubleshoot DirectAccess IP-HTTPS error 0x80090326, perform a network trace on the DirectAccess client and observe the TLS handshake for clues as to which configuration error is the culprit. If the TLS handshake failure occurs immediately after the client sends a Client Hello, it is likely that the ADC does not have null cipher suites enabled.

Troubleshooting DirectAccess IP-HTTPS Error 0x80090326

If the TLS handshake failure occurs after the Server Hello, it is likely that the ADC is configured to perform client certificate authentication incorrectly, or the client does not have a valid certificate.

Troubleshooting DirectAccess IP-HTTPS Error 0x80090326

IP-HTTPS error 0x80090326 can also occur if an intermediary device is performing SSL/TLS inspection or otherwise tampering with the TLS request. It can also happen if the edge firewall and/or NAT device is forwarding IP-HTTPS connections to the wrong internal server, or if the firewall itself is responding to the HTTPS connection request. Remember, just because the server is responding on TCP port 443 doesn’t necessarily mean that it is the DirectAccess server responding!

Additional Information

Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

Troubleshooting DirectAccess IP-HTTPS Error 0x2af9

DirectAccess Troubleshooting Consulting Services

Implementing DirectAccess with Windows Server 2016

Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

A Windows 7 or Windows 8.x/10 client may fail to establish a DirectAccess connection using the IP-HTTPS IPv6 transition technology. When troubleshooting this issue, running ipconfig.exe shows that the media state for the tunnel adapter iphttpsinterface is Media disconnected.

Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

Running the Get-NetIPHttpsState PowerShell command on Windows 8.x/10 clients or the netsh interface httpstunnel show interface command on Windows 7 clients returns an error code of 0x90320, with an interface status Failed to connect to the IPHTTPS server; waiting to reconnect.

Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

Error code 0x90320 translates to SEC_I_INCOMPLETE_CREDENTIALS, indicating the client was unable to authenticate to the DirectAccess server during the TLS handshake when establishing the IP-HTTPS IPv6 transition tunnel. This occurs when the DirectAccess server or an Application Delivery Controller (ADC) is configured to perform client certificate authentication for IP-HTTPS connections. The client may fail to authenticate if it does not have a valid certificate issued by the organization’s internal certification authority (CA) or if the DirectAccess server or ADC is configured to perform IP-HTTPS client authentication incorrectly.

To resolve this issue, ensure that a valid certificate is installed on the DirectAccess client. In addition, ensure that the DirectAccess server or ADC is configured to use the correct CA when authenticating clients establishing IP-HTTPS connections.

Additional Information

DirectAccess IP-HTTPS Preauthentication 

DirectAccess IP-HTTPS Preauthentication using Citrix NetScaler

DirectAccess SSL Offload and IP-HTTPS preauthentication using Citrix NetScaler 

DirectAccess IP-HTTPS preauthentication using F5 BIG-IP 

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Introduction

Communication between the DirectAccess client and server takes place exclusively over IPv6. When DirectAccess servers and/or clients are on the IPv4 Internet, an IPv6 transition technology must be employed to allow those clients to connect to the DirectAccess server. DirectAccess deployment best practices dictate that only the IP-HTTPS IPv6 transition technology be used. IP-HTTPS uses SSL/TLS for server authentication and optionally encryption. To improve security and performance for IP-HTTPS, an Application Delivery Controller (ADC) like the Citrix NetScaler can be configured to perform SSL offloading and client preauthentication for DirectAccess IP-HTTPS connections.

Please note that the following caveats apply when enabling SSL offload for DirectAccess clients:

  • Enabling SSL offload and IP-HTTPS preauthentication on an ADC for DirectAccess is formally unsupported by Microsoft.
  • SSL offload should not be enabled with DirectAccess is configured to use one-time password (OTP) authentication. Offloading SSL will break OTP functionality.

IP-HTTPS Challenges

The IP-HTTPS IPv6 transition technology is a simple and effective way to allow DirectAccess clients and servers to communicate by encapsulating IPv6 traffic in HTTP and routing it over the public IPv4 Internet. However, there are two critical issues with the default implementation of IP-HTTPS in DirectAccess. One is a security issue, the other affects performance.

Security

The DirectAccess server does not authenticate clients establishing IP-HTTPS connections. This could allow an unauthorized client to obtain an IPv6 address from the DirectAccess server using the IPv6 Neighbor Discovery (ND) process. With a valid IPv6 address, the unauthorized user could perform internal network reconnaissance or launch a variety of Denial of Service (DoS) attacks on the DirectAccess infrastructure and connected clients. More details here.

Performance

Windows 7 DirectAccess clients use encrypted cipher suites when establishing IP-HTTPS connections. However, the payload being transported is already encrypted using IPsec. This double encryption increases resource utilization on the DirectAccess server, reducing performance and limiting scalability. More details here.


Note: Beginning with Windows Server 2012 and Windows 8, Microsoft introduced support for null encryption for IP-HTTPS connections. This eliminates the needless double encryption, greatly improving scalability and performance for DirectAccess clients using IP-HTTPS.


SSL Offload for DirectAccess IP-HTTPS

The Citrix NetScaler can be configured to perform SSL offload to improve performance for Windows 7 DirectAccess clients using IP-HTTPS. Since DirectAccess does not natively support SSL offload, the NetScaler must be configured in a non-traditional way. While the NetScaler will be configured to terminate incoming IP-HTTPS SSL connections, it must also use SSL for the back-end connection to the DirectAccess server. However, the NetScaler will be configured only to use null cipher suites when connecting to the DirectAccess server. Even though Windows 7 clients will still perform double encryption to the NetScaler, this configuration effectively offloads from the server the heavy burden of double encrypting every IP-HTTPS connection for all connected DirectAccess clients. This results in reduced CPU utilization on the DirectAccess server, yielding better scalability and performance.

SSL Offload and Windows 8.x/10 Clients

Offloading SSL for Windows 8.x/10 clients will not improve performance because they already use null cipher suites for IP-HTTPS when connecting to a Windows Server 2012 or later DirectAccess server. However, terminating SSL on the NetScaler is still required to perform IP-HTTPS preauthentication.

Supported NetScaler Platforms for DirectAccess SSL Offloading

The following configuration for Citrix NetScaler can be performed on any release of the VPX virtual ADC platform. However, be advised that there is a known issue with older releases on the MDX and SDX hardware platforms that will prevent this from working. For MDX and SDX deployments, upgrading to release 11.1 build 50.10 or later will be required.

Configure Citrix NetScaler for IP-HTTPS SSL Offload

To enable SSL offloading for DirectAccess IP-HTTPS on the Citrix NetScaler, open the NetScaler management console, expand Traffic Management and Load Balancing, and then perform the following procedures in order.

Add Servers

  1. Click Servers.
  2. Click Add.
  3. In the Name field enter a descriptive name for the first DirectAccess server.
  4. Select IP Address.
  5. In the IP Address field enter the IP address of the first DirectAccess server.
  6. Click Create.
  7. Repeat these steps for any additional servers in the load-balanced cluster.

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Add Services

  1. Click Services.
  2. Click Add.
  3. In the Service Name field enter a descriptive name for the service.
  4. Select Existing Server from the Server drop-down list.
  5. Choose the first DirectAccess server in the cluster.
  6. Choose SSL from the Protocol drop-down list.
  7. Click Ok.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler
  8. Edit SSL Parameters.
    1. In the Protocol section uncheck SSLv3.
    2. Click Ok.
  9. Edit SSL Ciphers.
    1. Click Remove All.
    2. Click Add.
    3. Type NULL in the Search Ciphers box.
    4. Check the box next to the first entry for SSL3-NULL-SHA.
    5.  Click the right arrow to add the cipher to the list.
    6. Click Ok.
    7. Click Done.
    8. Repeat these steps for any additional servers in the load-balanced cluster.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

A warning message may be displayed indicating that no usable ciphers are configured on the SSL vserver/service. This message can be safely ignored.

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Add Virtual Server

  1. Click Virtual Servers.
    1. Click Add.
    2. In the Name field enter a descriptive name for the virtual server.
    3. Choose SSL from the Protocol drop-down list.
    4. In the IP Address field enter the IP address for the virtual server.
    5. Click Ok.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

      Note: When enabling load balancing in DirectAccess, the IP address assigned to the first DirectAccess server is reallocated for use as the load balancing Virtual IP Address (VIP). Ideally this IP address will be assigned to the load balancing virtual server on the NetScaler. However, this is not a hard requirement. It is possible to configure the VIP on the NetScaler to reside on any subnet that the load balancer has an interface to. More details here.


  2. In the Services and Groups section click No Load Balancing Virtual Server Service Binding.
    1. Click on the Select Service field.
    2. Check all DirectAccess server services and click Select.
    3. Click Bind.
    4. Click Continue.
  3. In the Certificate section click No Server Certificate.
    1. Click on the Select Server Certificate field.
    2. Choose the certificate to be used for DirectAccess IP-HTTPS.
    3. Click Select.
    4. Click Bind.
    5. Click Continue.
  4. Edit SSL Ciphers.
    1. Click Remove All.
    2. Click Add.
    3. Type ECDHE in to the Search Ciphers box.
    4. Check the box next to TLS1-ECDHE-RSA-AES128-SHA.
    5. Click the right arrow to add the cipher to the list.
    6. Type NULL in to the Search Ciphers box.
    7. Check the box next to SSL3-NULL-SHA.
    8. Click the right arrow to add the cipher to the list.
    9. Click Ok.
    10. Click Done.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

      Note: If Windows 8.x/10 clients are supported exclusively, SSL3-NULL-SHA is the only cipher suite required to be configured on the virtual server. If Windows 7 client support is required, the TLS1-ECDHE-RSA-AES128-SHA cipher suite should also be configured on the virtual server.


  5. Edit SSL Parameters.
    1. Uncheck SSLv3.
    2. Click Ok.

      Note: If Windows 8.x/10 clients are supported exclusively, TLSv1 can also be unchecked on the virtual server. If Windows 7 client support is required, TLSv1 must be enabled.


  6. In the Advanced Settings section click Persistence.
    1. Choose SSLSESSION.
    2. Enter 10 minutes for the Time-out (mins) value.
    3. Click Ok.
    4. Click Done.

Optional IP-HTTPS Preauthentication

To enable IP-HTTPS preauthentication to prevent unauthorized network access, perform the following procedures on the Citrix NetScaler appliance.

  1. Expand Traffic Management, Load Balancing, and then click Virtual Servers.
  2. Select the DirectAccess virtual server and click Edit.
    1. In the Certificate section click No CA Certificate.
    2. Click the Select CA Certificate field.
    3. Choose the certificate for the CA that issues certificates to DirectAccess clients and servers.

      Note: The CA certificate used for DirectAccess can be found by opening the Remote Access Management console, clicking Edit on Step 2, and then clicking Authentication. Alternatively, the CA certificate can be found by running the following PowerShell command.

      (Get-RemoteAccess).IPsecRootCertificate | Format-Table Thumbprint


    4. Click Select.
    5. Choose CRL Optional from the CRL and OCSP Check drop-down list.
    6. Click Bind.
  3. Edit SSL Parameters.
    1. Check the box next to Client Authentication.
    2. Choose Mandatory from the Client Certificate drop-down list.
    3. Click Ok.
    4. Click Done.
      DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Summary

Leveraging the advanced capabilities of the Citrix NetScaler ADC can improve performance when supporting Windows 7 clients and enhance security for all DirectAccess clients using IP-HTTPS. In terms of supportability, all of the changes described in this article are completely transparent and do not alter the native DirectAccess client or server configuration. If a Microsoft support engineer declines support due to this configuration, switching from SSL offload to SSL bridge is all that’s required to restore full supportability.

Additional Resources

NetScaler release 11.1 build 50.10 (requires login) – https://www.citrix.com/downloads/netscaler-adc/firmware/release-111-build-5010

Release notes for build 50.10 of NetScaler 11.1 release – https://www.citrix.com/content/dam/citrix/en_us/documents/downloads/netscaler-adc/NS_11_1_50_10.html

VIDEO: Enable Load Balancing for DirectAccess – https://www.youtube.com/watch?v=3tdqgY9Y-uo

DirectAccess IP-HTTPS preauthentication using F5 BIG-IP – https://directaccess.richardhicks.com/2016/05/23/directaccess-ip-https-preauthentication-using-f5-big-ip/

DirectAccess SSL offload for IP-HTTPS using F5 BIG-IP – https://directaccess.richardhicks.com/2013/07/10/ssl-offload-for-ip-https-directaccess-traffic-from-windows-7-clients-using-f5-big-ip/

Implementing DirectAccess with Windows Server 2016 book – http://directaccessbook.com/

Migrating DirectAccess from NLB to External Load Balancer


Introduction

Migrating DirectAccess from NLB to External Load BalancerMultiple DirectAccess servers can be deployed in a load-balanced cluster to eliminate single crucial points of failure and to provide scalability for the remote access solution. Load balancing can be enabled using the integrated Windows Network Load Balancing (NLB) or an external physical or virtual load balancer.

NLB Drawbacks and Limitations

NLB is often deployed because it is simple and inexpensive. However, NLB suffers from some serious drawbacks that limit its effectiveness in all but the smallest deployments. For example, NLB uses network broadcasts to communicate cluster heartbeat information. Each node in the cluster sends out a heartbeat message every second, which generates a lot of additional network traffic on the link and reduces performance as more nodes are added. Scalability is limited with NLB too, as only 8 nodes are supported, although the practical limit is 4 nodes. Further, NLB supports only round-robin connection distribution.

External Load Balancer

A better alternative is to implement a dedicated physical or virtual load balancing appliance. A purpose-built load balancer provides additional security, greater scalability (up to 32 nodes per cluster), improved performance, and fine-grained traffic control.

Migrate from NLB to ELB

It is possible to migrate to an external load balancer (ELB) after NLB has already been configured. To do this, follow the guidance provided in my latest blog post on the KEMP Technologies blog entitled “Migrating DirectAccess from NLB to KEMP LoadMaster Load Balancers”.

Migrating DirectAccess from NLB to External Load Balancer

Additional Resources

DirectAccess Deployment Guide for KEMP LoadMaster Load Balancers

Migrating DirectAccess from NLB to KEMP LoadMaster Load Balancers

Load Balancing DirectAccess with KEMP LoadMaster Load Balancers

DirectAccess Load Balancing Tips and Tricks Webinar with KEMP Technologies

DirectAccess Single NIC Load Balancing with KEMP LoadMaster Load Balancer

Configuring the KEMP LoadMaster Load Balancer for DirectAccess NLS

Enable DirectAccess Load Balancing Video

Implementing DirectAccess with Windows Server 2016 Book

Deploying DirectAccess in Microsoft Azure

Introduction

DirectAccess Now a Supported Workload in Microsoft AzureMany organizations are preparing to implement DirectAccess on Microsoft’s public cloud infrastructure. Deploying DirectAccess in Azure is fundamentally no different than implementing it on premises, with a few important exceptions (see below). This article provides essential guidance for administrators to configure this unique workload in Azure.

Important Note: There has been much confusion regarding the supportability of DirectAccess in Azure. Historically it has not been supported. Recently, it appeared briefly that Microsoft reversed their earlier decision and was in fact going to support it. However, the Microsoft Server Software Suport for Microsoft Azure Virtual Machines document has once again been revised to indicate that DirectAccess is indeed no longer formally supported on Azure. More details can be found here.

Azure Configuration

The following is guidance for configuring network interfaces, IP address assignments, public DNS, and network security groups for deploying DirectAccess in Azure.

Virtual Machine

Deploy a virtual machine in Azure with sufficient resources to meet expected demand. A minimum of two CPU cores should be provisioned. A VM with 4 cores is recommended. Premium storage on SSD is optional, as DirectAccess is not a disk intensive workload.

Network Interfaces

It is recommended that an Azure VM with a single network interface be provisioned for the DirectAccess role. This differs from on-premises deployments where two network interfaces are preferred because deploying VMs in Azure with two NICs is prohibitively difficult. At the time of this writing, Azure VMs with multiple network interfaces can only be provisioned using PowerShell, Azure CLI, or resource manager templates. In addition, Azure VMs with multiple NICs cannot belong to the same resource group as other VMs. Finally, and perhaps most importantly, not all Azure VMs support multiple NICs.

Internal IP Address

Static IP address assignment is recommended for the DirectAccess VM in Azure. By default, Azure VMs are initially provisioned using dynamic IP addresses, so this change must be made after the VM has been provisioned. To assign a static internal IP address to an Azure VM, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Network Interfaces.
  4. Click on the network interface assigned to the VM.
  5. Under Settings click IP configurations.
  6. Click Ipconfig1.
  7. In the Private IP address settings section choose Static for the assignment method.
  8. Enter an IP address for the VM.
  9. Click Save.

Deploying DirectAccess in Microsoft Azure

Public IP Address

The DirectAccess VM in Azure must have a public IP address assigned to it to allow remote client connectivity. To assign a public IP address to an Azure VM, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Network Interfaces.
  4. Click on the network interface assigned to the VM.
  5. Under Settings click IP configurations.
  6. Click Ipconfig1.
  7. In the Public IP address settings section click Enabled.
  8. Click Configure required settings.
  9. Click Create New and provide a descriptive name for the public IP address.
  10. Choose an address assignment method.
  11. Click Ok and Save.

Deploying DirectAccess in Microsoft Azure

Deploying DirectAccess in Microsoft Azure

Public DNS

If the static IP address assignment method was chosen for the public IP address, create an A resource record in public DNS that resolves to this address. If the dynamic IP address assignment method was chosen, create a CNAME record in public DNS that maps to the public hostname for the DirectAccess server. To assign a public hostname to the VM in Azure, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Overview.
  4. Click Public IP address/DNS name label.Deploying DirectAccess in Microsoft Azure
  5. Under Settings click Configuration.
  6. Choose an assignment method (static or dynamic).
  7. Enter a DNS name label.
  8. Click Save.

Deploying DirectAccess in Microsoft Azure

Note: The subject of the SSL certificate used for the DirectAccess IP-HTTPS listener must match the name of the public DNS record (A or CNAME) entered previously. The SSL certificate does not need to match the Azure DNS name label entered here.

Network Security Group

A network security group must be configured to allow IP-HTTPS traffic inbound to the DirectAccess server on the public IP address. To make the required changes to the network security group, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Network interfaces.
  4. Click on the network interface assigned to the VM.
  5. Under Settings click Network security group.
  6. Click the network security group assigned to the network interface.
  7. Click Inbound security rules.
  8. Click Add and provide a descriptive name for the new rule.
  9. Click Any for Source.
  10. From the Service drop-down list choose HTTPS.
  11. Click Allow for Action.
  12. Click Ok.

Deploying DirectAccess in Microsoft Azure

Note: It is recommended that the default-allow-rdp rule be removed if it is not needed. At a minimum, scope the rule to allow RDP only from trusted hosts and/or networks.

DirectAccess Configuration

When performing the initial configuration of DirectAccess using the Remote Access Management console, the administrator will encounter the following warning message.

“One or more network adapters should be configured with a static IP address. Obtain a static address and assign it to the adapter.”

Deploying DirectAccess in Microsoft Azure

This message can safely be ignored because Azure infrastructure handles all IP address assignment for hosted VMs.

The public name of the DirectAccess server entered in the Remote Access Management console must resolve to the public IP address assigned to the Azure VM, as described previously.

Deploying DirectAccess in Microsoft Azure

Additional Considerations

When deploying DirectAccess in Azure, the following limitations should be considered.

Load Balancing

It is not possible to enable load balancing using Windows Network Load Balancing (NLB) or an external load balancer. Enabling load balancing for DirectAccess requires changing static IP address assignments in the Windows operating system directly, which is not supported in Azure. This is because IP addresses are assigned dynamically in Azure, even when the option to use static IP address assignment is chosen in the Azure management portal. Static IP address assignment for Azure virtual machines are functionally similar to using DHCP reservations on premises.

Deploying DirectAccess in Microsoft Azure

Note: Technically speaking, the DirectAccess server in Azure could be placed behind a third-party external load balancer for the purposes of performing SSL offload or IP-HTTPS preauthentication, as outlined here and here. However, load balancing cannot be enabled in the Remote Access Management console and only a single DirectAccess server per entry point can be deployed.

Manage Out

DirectAccess manage out using native IPv6 or ISATAP is not supported in Azure. At the time of this writing, Azure does not support IPv6 addressing for Azure VMs. In addition, ISATAP does not work due to limitations imposed by the underlying Azure network infrastructure.

Summary

For organizations moving infrastructure to Microsoft’s public cloud, formal support for the DirectAccess workload in Azure is welcome news. Implementing DirectAccess in Azure is similar to on-premises with a few crucial limitations. By following the guidelines outlined in this article, administrators can configure DirectAccess in Azure to meet their secure remote access needs with a minimum of trouble.

Additional Resources

Implementing DirectAccess in Windows Server 2016
Fundamentals of Microsoft Azure 2nd Edition
Microsoft Azure Security Infrastructure
DirectAccess Multisite with Azure Traffic Manager
DirectAccess Consulting Services

DirectAccess Load Balancing Tips and Tricks Webinar

KEMP Technologies LoadMaster Load BalancerEnabling load balancing for DirectAccess deployments is crucial for eliminating single points of failure and ensuring the highest levels of availability for the remote access solution. In addition, enabling load balancing allows DirectAccess administrators to quickly and efficiently add capacity in the event more processing power is required.

DirectAccess includes support for load balancing using integrated Windows Network Load Balancing (NLB) and external load balancers (physical or virtual). External load balancers are the recommended choice as they provide superior throughput, more granular traffic distribution, and greater visibility. External load balancers also more scalable, with support for much larger DirectAccess server clusters, up to 32 nodes. NLB is formally limited to 8 nodes, but because it operates at layer 2 in the OSI model and relies on broadcast heartbeat messages, it is effectively limited to 4 nodes.

The KEMP Technologies LoadMaster load balancer is an excellent choice for load balancing the DirectAccess workload. To learn more about configuring the LoadMaster with DirectAccess, join me for a free live webinar on Tuesday, August 16 at 10:00AM PDT where I’ll discuss DirectAccess load balancing in detail. I will also be sharing valuable tips, tricks, and best practices for load balancing DirectAccess.

DirectAccess Load Balancing Tips and Tricks Webinar

Don’t miss out. Register today!

Additional Resources

DirectAccess Load Balancing Overview

Load Balancing DirectAccess with the KEMP Loadmaster Load Balancer

Maximize your investment in Windows 10 with DirectAccess and the KEMP LoadMaster Load Balancer

KEMP LoadMaster DirectAccess Deployment Guide

DirectAccess Load Balancing Video

DirectAccess Load Balancing VideoConfiguring load balancing in DirectAccess is essential for eliminating single points of failure and ensuring the highest level of availability for the solution. The process of enabling load balancing for DirectAccess can be confusing though, as it involves the reassignment of IP addresses from the first server to the virtual IP address (VIP) for the cluster.

In this video I demonstrate how to enable DirectAccess load balancing and explain in detail how IP address assignment works for both Network Load Balancing (NLB) and external load balancers (ELB).

Windows 10 Multisite DirectAccess with GSLB Webinar

Kemp Technologies LoadMaster Load BalancerWindows 10 clients include full support for all enterprise DirectAccess scalability and redundancy features, including automatic site selection and transparent failover for multisite deployments. However, the native site selection process is limited in functionality and often yields unexpected results.

To provide better client support for multisite DirectAccess, a Global Server Load Balancer (GSLB) solution such as the Kemp Technologies LoadMaster GEO can be deployed. Using the LoadMaster’s GSLB functionality can significantly enhance multisite site selection for Windows 10 clients. In addition, it can be used to enable new scenarios not supported natively such as weighted distribution and active/passive failover.

Kemp Technologies LoadMaster Load Balancer

To learn more about how address the shortcomings of DirectAccess multisite using the Kemp LoadMaster GEO, join me for a live webinar on Thursday, July 14, 2106 at 10:00AM EDT where I’ll discuss the following topics.

  • How Global Server Load Balancing (GSLB) works
  • How Windows 10 clients choose an entry point
  • Understand the limitations of the native site selection process for Windows 10 clients
  • How to use the Kemp LoadMaster GEO to provide true geographic redundancy
  • How to enable active/passive failover for disaster recovery

You can register for this free live webinar here.

DirectAccess IP-HTTPS Preauthentication


Introduction

DirectAccess IP-HTTPS PreauthenticationRecently I’ve written about the security challenges with DirectAccess, specifically around the use of the IP-HTTPS IPv6 transition technology. In its default configuration, the DirectAccess server does not authenticate the client when an IP-HTTPS transition tunnel is established. This opens up the possibility of an unauthorized user launching Denial-of-Service (DoS) attacks and potentially performing network reconnaissance using ICMPv6. More details on this can be found here.

Mitigation

The best way to mitigate these security risks is to implement an Application Delivery Controller (ADC) such as the F5 BIG-IP Local Traffic Manager or the Citrix NetScaler. I’ve documented how to configure those platforms here and here.

No ADC?

For those organizations that do not have a capable ADC deployed, it is possible to configure the IP-HTTPS listener on the Windows Server 2012 R2 server itself to perform preauthentication.

Important Note: Making the following changes on the DirectAccess server is not formally supported. Also, this change is incompatible with one-time passwords (OTP)  and should not be performed if strong user authentication is enabled. In addition, null cipher suites will be disabled, resulting in reduced scalability and degraded performance for Windows 8.x and Windows 10 clients. Making this change should only be done if a suitable ADC is not available.

Configure IP-HTTPS Preauthentication

To configure the DirectAccess server to perform preauthentication for IP-HTTPS connections, open an elevated PowerShell command window and enter the following command.

ls Cert:\LocalMachine\My

DirectAccess IP-HTTPS Preauthentication

Copy the thumbprint that belongs to the SSL certificate assigned to the IP-HTTPS listener. Open an elevated command prompt window (not a PowerShell window!) and enter the following commands.

netsh http delete sslcert ipport=0.0.0.0:443
netsh http add sslcert ipport=0.0.0.0:443 certhash=[thumbprint]
appid={5d8e2743-ef20-4d38-8751-7e400f200e65}
dsmapperusage=enable clientcertnegotiation=enable

DirectAccess IP-HTTPS Preauthentication

For load-balanced clusters and multisite deployments, repeat these steps on each DirectAccess server in the cluster and/or enterprise.

Summary

Once these changes have been made, only DirectAccess clients that have a computer certificate with a subject name that matches the name of its computer account in Active Directory will be allowed to establish an IP-HTTPS transition tunnel connection.

Configure Citrix NetScaler for DirectAccess NLS

DirectAccess and Citrix NetScaler WebinarIntroduction

The Network Location Server (NLS) is a crucial DirectAccess supporting infrastructure component. It is secure web server that DirectAccess clients use to determine if they are inside or outside of the corporate network.

NLS Availability

The NLS should be highly available. If this service is not available, DirectAccess clients on the internal network will think they are outside and attempt to establish a DirectAccess connection. Typically, this results in the DirectAccess client not being able to reach internal resources by hostname. Full connectivity for DirectAccess clients on the internal network will not be restored until the NLS is online.

It is recommended that the NLS be deployed in a load-balanced cluster for high availability. However, this requires deploying multiple servers, adding more cost, complexity, and management overhead to the solution.

NLS and Citrix NetScaler

Configuring the Citrix NetScaler to serve as the NLS is an attractive alternative to deploying additional servers for this role. Using the NetScaler for the NLS reduces costs by leveraging existing infrastructure. In addition, the NetScaler requires less servicing than a typical Windows server, and is often itself already highly available.

Configure Citrix NetScaler

To configure the NetScaler to serve as a DirectAccess NLS, open the NetScaler management console, expand AppExpert, and then select Actions. Click Add, provide a descriptive name for the responder action, and then enter the following in the Expression field and click Create.

"HTTP/1.0 200 OK" +"\r\n\r\n" + "DirectAccess Network Location Server (NLS)" + "\r\n"

Configure Citrix NetScaler for DirectAccess NLS

Select Policies, click Add, and then provide a descriptive name for the responder policy. Enter HTTP.REQ.IS_VALID in the Expression field and click Create.

Configure Citrix NetScaler for DirectAccess NLS

Expand Traffic Management, expand Load Balancing and select Services. Click Add, provide a descriptive name for the service, choose New Server, and enter the IPv4 loopback address 127.0.0.1. Select SSL for the Protocol, enter a random port number for the Port and then click More.

Configure Citrix NetScaler for DirectAccess NLS

Uncheck the box next to Health Monitoring and click Ok and Done.

Configure Citrix NetScaler for DirectAccess NLS

Select Virtual Servers and click Add. Provide a descriptive name for the virtual server, select SSL for the Protocol, enter an IP address for the virtual server and click Ok.

Configure Citrix NetScaler for DirectAccess NLS

Under Services and Service Groups click No Load Balancing Virtual Server Service Binding.

Configure Citrix NetScaler for DirectAccess NLS

Click to select a service, choose the service created previously and click Ok, Bind and Ok.

Configure Citrix NetScaler for DirectAccess NLS

Under Certificates click No Server Certificate.

Configure Citrix NetScaler for DirectAccess NLS

Click to select a server certificate, choose the SSL certificate to be used by the NLS and click Ok, Bind, and Ok.

Configure Citrix NetScaler for DirectAccess NLS

Under Advanced click Policies, and then click the + icon. From the Choose Policy drown-list choose Responder and click Continue. Click to select a Policy Binding and choose the responder policy created previously. Click Ok, Bind, and Done.

Configure Citrix NetScaler for DirectAccess NLS

Testing NLS Functionality

Open a web browser on a client connected to the internal network and browse to the NLS URL. Ensure that there are no certificate errors and that the NetScaler is responding with the configured web page.

Configure Citrix NetScaler for DirectAccess NLS

Summary

The Network Location Server (NLS) is an important, and often overlooked, supporting infrastructure component for DirectAccess. It is used by DirectAccess clients to determine their network location. If it is unavailable for any reason it can be very disruptive. Ensuring that the NLS is highly available is critical. Configuring the NLS on the Citrix NetScaler can be a cost-effective alternative to deploying additional servers, while at the same time reducing the chance of an outage due to NLS failure.

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