Always On VPN and Zero Trust Network Access (ZTNA)

Always On VPN and Zero Trust Network Access (ZTNA)

Zero Trust Network Access (ZTNA) is a term that administrators are likely familiar with, as it is one of the hottest marketing buzzwords in circulation today. ZTNA can mean different things depending on the deployment scenario. ZTNA is fundamentally about enforcing the principle of least privilege for endpoints connecting remotely to the corporate network when it comes to enterprise mobility and remote access.

Trusted Access

Historically, VPNs and even DirectAccess granted full, unrestricted network access to authenticated devices and users. Once the endpoint has an IP address, and in the absence of other controls (routing limitations, firewall access controls, etc.), the user could access any resource on the internal network. The rationale was that authenticated devices and users should be considered “trusted”.

Limitations

The Trusted Access model has some significant limitations. It assumes that all traffic from authorized users and devices is legitimate. However, if an endpoint is compromised, an attacker has broad access to the internal network, which is not ideal from a security perspective.

Zero Trust

Zero Trust Network Access is a concept where administrators define explicitly the minimum level of access required to support remote workers. Instead of granting full network access to the endpoint, controlling access using fine-grained policies is enforced on the VPN connection. Configuring limited network access for Always On VPN clients dramatically reduces exposure of the internal network to compromised endpoints.

ZTNA Management

There is a significant management burden associated with this approach, however. Administrators must identify each application requiring VPN access and determine all associated protocols and ports to be allowed, and internal resources to which they will communicate. Although this task isn’t difficult if clients require access to a small subset of internal resources, it can be a substantial undertaking if clients require access to many internal resources from numerous client applications.

Moving Targets

Making things more challenging is that application and network infrastructure often change constantly, requiring administrators to manage network access continually to ensure application availability. When adding new applications or changing the internal infrastructure, updating the configuration on all remote endpoints will be required.

Updating Always On VPN configuration for devices managed with Microsoft Endpoint Manager (formerly Intune) isn’t difficult. However, it can be more challenging when using PowerShell with System Center Configuration Manager (SCCM) or another endpoint management platform.

Traffic Filters

ZTNA can be configured with Always On VPN using Traffic Filters. With Traffic Filters, administrators can apply fine-grained access control for VPN traffic based on a combination of the following.

  • Source IP address (IP address, address range, or subnet)
  • Destination IP address (IP address, address range, or subnet)
  • Protocol (TCP, UDP, IP, etc.)
  • Source Port
  • Destination Port

Endpoint Manager Configuration

Configuring Traffic Filters for Always On VPN connections can be performed using Microsoft Endpoint Manager. Open the Endpoint Manager management console (https://endpoint.microsoft.com), navigate to the Always On VPN device configuration profile, then perform the following steps.

  1. Expand App and Traffic Rules.
  2. Click Add next to Network traffic rules for this VPN connection.
  1. Enter a descriptive name in the Name field.
  2. Select Split tunnel from the Rule type drop-down list.
  3. Enter “6” in the Protocol field.
  4. Enter “3389” in the Lower port and Upper port fields in the Remote port ranges section.
  5. Enter an IPv4 address in the Lower IPv4 address field.
  6. Enter an IPv4 address in the Upper IPv4 address field. Enter the same IPv4 address as the lower address to specify a single host.
  7. Click Save.

The example above shows a traffic filter restricting access to TCP port 3389 (Remote Desktop Protocol) from all VPN clients to the 172.16.0.0/24 network.

Note: Repeat these steps to create as many traffic filters as required for any processes or applications that must communicate over the Always On VPN connection.

XML Configuration

Traffic Filters can also be configured using custom XML. To implement the same Traffic Filter described previously, add the following code between the <VPNProfile> and </VPNProfile> tags in your XML configuration file.

<TrafficFilter>
   <Protocol>6</Protocol>
   <RemotePortRanges>3389</LocalPortRanges>
   <RemoteAddressRanges>172.16.0.0/24</RemoteAddressRanges>
</TrafficFilter>

Note: Address ranges used in Traffic Filters can be defined using CIDR notation in XML, but they are not supported using Microsoft Endpoint Manager today.

Default Deny

When configuring a Traffic Filter for an Always On VPN profile, an implicit “deny all” rule is automatically enabled. Any traffic not explicitly defined in a Traffic Filter will be denied, including unsolicited inbound traffic, which has crucial implications for the device tunnel because it is used commonly for system management of remote devices.

Direction

Traffic Filters are enabled for the Outbound direction only, by default. Beginning with Windows 10 2004, Microsoft introduced support for Inbound traffic filters. Before Windows 10 2004, configuring a Traffic Filter on the device tunnel would break manage-out scenarios by denying all unsolicited inbound network access.

As of this writing, configuring inbound Traffic Filters using Microsoft Endpoint Manager is not supported. They are only configurable using custom XML.

To implement a Traffic Filter to allow inbound RDP access from the internal network over the device tunnel, add the following code between the <VPNProfile> and </VPNProfile> tags in your XML configuration file.

<TrafficFilter>
   <Protocol>6</Protocol>
   <LocalPortRanges>3389</LocalPortRanges>
   <RemoteAddressRanges>172.16.0.0/16</RemoteAddressRanges>
   <Direction>Inbound</Direction>
</TrafficFilter>

Note: When configuring inbound Traffic Filters, specify the port of the listening process or application using the LocalPortRanges field.

Application Filters

Administrators can combine Application Filters with Traffic Filters to control network access over the Always On VPN connection even more granularly. Applications can be defined by the following.

  • Package Family Name (PFN) – This is the unique name of a Microsoft Store application. Use the Get-AppxPackage PowerShell command to find the PFN for an application.
  • File Path – This is the full path to any executable on the file system. For example, c:\Windows\System32\mstsc.exe.
  • SYSTEM – This allows Windows kernel-mode drivers (such as ping.exe and net.exe) to send traffic over the Always On VPN connection.

As of this writing, configuring Application Filters using Microsoft Endpoint Manager is not supported. They are only configurable using custom XML.

Application Filter Examples

Below are three examples showing different Application Filters based on file path, Package Family Name, and SYSTEM.

File Path

This example shows a Traffic Filter configured to allow RDP access to an internal subnet using the native Windows Remote Desktop client (mstsc.exe).

<TrafficFilter>
   <App>
      <Id>C:\Windows\System32\mstsc.exe</Id>
   </App>
   <Protocol>6</Protocol>
   <RemotePortRanges>3389</RemotePortRanges>
   <RemoteAddressRanges>172.16.0.0/24</RemoteAddressRanges>
</TrafficFilter>

Package Family Name

This example shows a Traffic Filter configured to allow RDP access to an internal subnet using the Microsoft Windows Store Remote Desktop client.

<TrafficFilter>
   <App>
      <Id>Microsoft.RemoteDesktop_8wekyb3d8bbwe</Id>
   </App>
   <Protocol>6</Protocol>
   <RemotePortRanges>3389</RemotePortRanges>
   <RemoteAddressRanges>172.16.0.0/24</RemoteAddressRanges>
</TrafficFilter>

SYSTEM

This example shows a Traffic Filter configured to allow the netsh.exe process access to an internal subnet.

<TrafficFilter>
   <App>
      <Id>SYSTEM</Id>
   </App>
   <Protocol>6</Protocol>
   <RemotePortRanges>445</RemotePortRanges>
   <RemoteAddressRanges>172.16.0.0/24</RemoteAddressRanges>
</TrafficFilter>

This example shows a Traffic Filter configured to allow the ping.exe process access to an internal subnet.

<TrafficFilter>
   <App>
      <Id>SYSTEM</Id>
   </App>
   <Protocol>1</Protocol>
   <RemoteAddressRanges>172.16.0.0/24</RemoteAddressRanges>
</TrafficFilter>

Note: Ping uses ICMP (IP protocol 1), which is a network layer protocol. As such, defining ports for the filter is not required.

IPv6 Compatibility

Sadly, the filtering techniques described in this article do not work when also configuring IPv6 on the Always On VPN connection. As of this writing, enabling Traffic Filters when an IPv6 address is assigned to the VPN interface is not supported. More details can be found here.

Always On VPN Traffic Filters and IPv6

Summary

Configuring Zero Trust Network Access (ZTNA) with Windows 10 Always On VPN is not trivial. Still, with attention to detail, it can be a highly effective tool to enforce fine-grained network access policies and reduce exposure of the internal network to compromised endpoints. Combining Traffic Filters with Application Filters allows administrators to tightly control Always On VPN access and ensure the principle of least privilege is applied.

Additional Information

Windows 10 Always On VPN Traffic Filters and IPv6

Windows 10 Always On VPN User Tunnel XML Configuration Reference File

Windows 10 Always On VPN Device Tunnel XML Configuration Reference File

Windows 10 Always On VPN VPNv2 CSP Reference

IP Protocol Numbers

Always On VPN Traffic Filters and IPv6

Always On VPN Windows Server RRAS Service Does Not Start

Using Traffic Filters with Always On VPN provides administrators the option to configure a true Zero Trust Network Access (ZTNA) solution for their field-based users and devices. By enabling traffic filtering, network access over the Always On VPN connection can be controlled using fine-grained policies. Traffic Filter rules can be configured to restrict access based source and destination IP addresses, protocols, and source and destination ports. Administrators can further restrict access based on the application generating the traffic.

IPv6

While testing these features recently, I learned that the Microsoft Endpoint Manager (formerly Intune) user interface does not appear to support IPv6 when configuring traffic filter rules. As you can see here, the UI explicitly asks for an IPv4 address and complains when entering an IPv6 address in the address field, as shown here.

Interestingly, it is possible to add IPv6 addresses in XML, as follows.

<TrafficFilter>
   <App>
      <Id>Microsoft.RemoteDesktop_8wekyb3d8bbwe</Id>
   </App>
   <Protocol>6</Protocol>
   <RemotePortRanges>3389</RemotePortRanges>
   <RemoteAddressRanges>2001:470:f109::/48</RemoteAddressRanges>
</TrafficFilter>

Connection Failure

Unfortunately, after loading the XML on a test client, the Always On VPN connection fails with the following error message.

“Can’t connect to <ConnectionName>. Catastrophic failure.”

In addition, the Application event log records an event ID 20227 from the RasClient source with the following error.

“The user <UserName> dialed a connection name <ConnectionName> which has failed. The error code returned on failure is -2147418113.”

Workaround

At this time, the only known workaround is to update the configuration on the RRAS server to use IPv4 addressing for VPN clients.

Summary

Unfortunately, IPv6 is still a second-class citizen when it comes to Always On VPN. Although enabling IPv6 works well in most common deployment scenarios, the Microsoft Endpoint Manager management console often fails to accept IPv6 entries in IP address fields. In addition, some advanced features such as traffic filtering are incompatible with IPv6.

Additional Information

Windows 10 Always On VPN and Zero Trust Network Access (ZTNA)

Windows 10 Always On VPN Windows Server RRAS Service Does Not Start

Always On VPN Proxy Server Configuration

Always On VPN Proxy Server Configuration

Web proxy servers are not as common today as they once were, but a few organizations still leverage them to provide secure Internet access for their employees. Commonly they are used to inspect and control Internet traffic and to enforce acceptable use policies. Some organizations may wish to extend this protection to Always On VPN clients in the field by enabling force tunneling. Administrators can define a web proxy server for Always On VPN connections globally for web traffic or individual websites or domains.

VPN Proxy

A VPN web proxy server can be defined when the Always On VPN user tunnel connection uses force tunneling. Although you can still configure a VPN web proxy server with split tunneling enabled, it will not work. It is only functional when force tunneling is in use.

Administrators can configure a VPN web proxy server using the Microsoft Endpoint Manager UI or custom XML deployed with Endpoint Manager or PowerShell. Administrators can define a VPN web proxy server explicitly, or a proxy automatic configuration (PAC) file can be specified.

Note: VPN proxy server settings only work when force tunneling is enabled. Force tunneling is an unsupported configuration for the device tunnel, making the global proxy server setting for the device tunnel unsupported.

Proxy Autoconfiguration

Perform the following steps to configure a VPN web proxy server with a PAC file in Endpoint Manager.

  1. Expand the Proxy section in the Configuration settings of the Always On VPN configuration profile.
  2. Enter the URL for the PAC file in the Automatic configuration script field. Be sure to include the port number in the URL when using a non-standard port.
  3. Leave the Address and Port number fields blank.
  4. Choose Enable or Disable from the Bypass proxy for local addresses drop-down list.

To configure a VPN web proxy server with a PAC file using custom XML, include the following code between the <VPNProfile> and </VPNProfile> tags in the Always On VPN XML configuration file.

Explicit Proxy

Perform the following steps to configure an explicit VPN web proxy server in Endpoint Manager.

  1. Enter the IP address, hostname, or fully qualified domain name (recommended) in the Address field.
  2. Enter the port number in the Port number field.
  3. Choose Enable or Disable from the Bypass proxy for local addresses drop-down list.

To configure an explicit VPN web proxy server using custom XML, include the following code between the <VPNProfile> and </VPNProfile> tags in the Always On VPN XML configuration file.

Namespace Proxy

Administrators can also define VPN web proxy servers on a per-namespace or per-hostname basis. Namespace VPN proxy servers can be helpful for scenarios where routing public websites over the Always On VPN connection is required. Most commonly, this is necessary because the public website restricts access to the IP address of the on-premises Internet gateway.

A namespace VPN proxy server is implemented using a Name Resolution Policy Table (NRPT) rule. At the time of this writing, a bug in Microsoft Endpoint Manager prevents administrators from deploying this option using the UI.

As you can see here, administrators can specify a proxy server as part of an NRPT rule in the Endpoint Manager UI. Notice this section of the UI validates the proxy FQDN correctly.

Always On VPN Proxy Server Configuration

However, when you try to save the configuration profile, Endpoint Manager returns the following error.

“Unable to save due to invalid data. Update your data then try again: ProxyServerUri must be a valid URL or be empty.”

Interestingly, when entering a URL such as http://proxy.lab.richardhicks.net:8080/ in the Proxy field, the Endpoint Manager UI accepts it and successfully validates. But according to the VPNv2 Configuration Service Provider (CSP) reference, the value must be entered as an IP address. A hostname or FQDN also works based on my testing. Entering a URL as shown in the example above will not work at all.

With that, the only way to implement a namespace VPN web proxy server is to use custom XML. To do this, include the following code between the <VPNProfile> and </VPNProfile> tags in the Always On VPN XML configuration file.

Include the leading “.” to specify the entire domain, as shown above. Omit the leading “.” to specify an individual host (for example, app.richardhicks.com). Repeat this section for each additional host or domain, as required.

Caveat

Unfortunately, the Microsoft Internet Explorer web browser is the only browser that functions with the namespace VPN web proxy server. All modern web browsers, including Microsoft Edge, ignore the namespace proxy setting entirely, which seriously limits this feature’s usefulness in most organizations today.

Workaround

If routing a public website over the Always On VPN tunnel is required, adding its IP address(es) to the Always On VPN connection’s routing table is needed. However, doing this presents some unique challenges, as public websites frequently have many IP addresses, which are often dynamically changing. Also, it is common for public websites to pull content from many different domains or use Content Delivery Networks (CDNs), making the problem of identifying which IP addresses to add to the Always On VPN connection’s routing table even more challenging. Further, administrators must update the client configuration each a public website’s IP address changes, adding significant management overhead.

Summary

Routing client Internet traffic through an on-premises web proxy server for Always On VPN clients works well when force tunneling is enabled. Administrators can explicitly define a web proxy server or use a proxy automatic configuration (PAC) file. All web browsers work without issue in this scenario. Using a namespace proxy is only effective when browsing with Microsoft Internet Explorer. All modern web browsers, including Microsoft Edge, ignore namespace proxy settings.

Additional Information

Windows 10 Always On VPN and the Name Resolution Policy Table (NRPT)

Windows 10 VPNv2 Configuration Service Provider (CSP) Reference

Windows 10 Always On VPN Client DNS Server Configuration

Removing Always On VPN Connections

Removing Always On VPN ConnectionsMuch has been written about provisioning Windows 10 Always On VPN client connections over the past few years. While the preferred method for deploying Always On VPN is Microsoft Intune, using PowerShell is often helpful for initial testing, and required for production deployment with System Center Configuration Manager (SCCM) or Microsoft Endpoint Manager (MEM). That said, there will invariably come a time when an administrator has to remove an Always On VPN connection. It is not as simple as you might think.

PowerShell

There are a variety of ways to remove an existing Always On VPN connection, with the quickest and simplest being PowerShell and the Remove-VpnConnection cmdlet.

Get-VpnConnection -Name ‘Always On VPN’ | Remove-VpnConnection -Force

There are several limitations to this method, however.

Active Connections

Administrators will quickly realize that PowerShell fails to remove a VPN connection that is currently connected. As shown here, attempting to remove an active VPN connection will return the following error message.

“The VPN connection [connection name] cannot be removed from the local user connections. Cannot delete a connection while it is connected.”

Removing Always On VPN Connections

Registry Artifacts

Removing Always On VPN connections using PowerShell commonly leaves behind registry artifacts that can potentially cause problems. For example, there are several Always On VPN-related registry entries in several locations including the HKLM\SOFTWARE\Microsoft\EnterpriseResourceManager\Tracked hive that may not be deleted when removing an Always On VPN connection. When provisioning a new Always On VPN connection after deleting one with the same name previously, the administrator may encounter the following error message.

“Unable to create [connection name] profile: A general error occurred that is not covered by a more specific error code.”

Removing Always On VPN Connections

Note: This error can also be caused by improperly formatted XML configuration files. More details here.

Remove-AovpnConnection Script

Veteran Always On VPN administrators are likely familiar with PowerShell scripts I’ve created called New-AovpnConneciton.ps1 and New-AovpnDeviceConnection.ps1, which are hosted on my GitHub. These scripts are adapted from code samples published by Microsoft to which I have included additional functionality. To address the limitations highlighted in this article I have published a new PowerShell script called Remove-AovpnConnection.ps1. It will remove any Always On VPN connection, even those that are currently active. It also includes logic to remove known registry artifacts common to Always On VPN. Download the script from GitHub and use the following syntax to remove an Always On VPN connection, established or not.

.\Remove-AovpnConnection.ps1 -ProfileName [connection name]

Running this PowerShell command will forcibly remove an Always On VPN connection. Use the -DeviceTunnel switch when removing a device tunnel connection (requires running in the system context). I have also included a -CleanUpOnly switch to remove registry artifacts when the VPN connection was previously removed using another method.

Updated Installation Scripts

I have also updated New-AovpnConnection.ps1 to include these registry clean up steps. This will prevent future errors when provisioning an Always On VPN client where a connection of the same name was removed previously.

Note: New-AovpnConnection.ps1 has also been updated to support device tunnel deployments. As such, I have deprecated New-AovpnDeviceConnection.ps1. Simply use New-AovpnConnection.ps1 with the -DeviceTunnel switch to deploy an Always On VPN device tunnel.

Additional Information

Windows 10 Always On VPN Device Tunnel Configuration using PowerShell

Troubleshooting Always On VPN Unable to Create Profile General Error

 

Always On VPN Force Tunneling with Office 365 Exclusions

Always On VPN Force Tunneling with Office 365 ExclusionsWith the COVID-19 global pandemic forcing nearly everyone to work from home these days, organizations that implemented force tunneling for their VPN clients are likely encountering unexpected problems. When force tunneling is enabled, all client traffic, including Internet traffic, is routed over the VPN tunnel. This often overloads the VPN infrastructure and causes serious slowdowns, which degrades the user experience and negatively impacts productivity. This is especially challenging because so many productivity applications like Microsoft Office 365 are optimized for Internet accessibility. It is one of the main reasons that force tunneling is not generally recommended.

Force Tunneling with Exceptions

When enabling split tunneling is not an option, administrators frequently ask about enabling force tunneling with some exceptions. The most common configuration is enabling force tunneling while still allowing Office 365 traffic to go outside of the tunnel. While this is something that third-party solutions do easily, it has been a challenge for Always On VPN. Specifically, Always On VPN has no way to route traffic by hostname or Fully-Qualified Domain Name (FQDN).

Exclusion Routes

To address this challenge, the administrator can configure Exclusion Routes. Exclusion Routes are supported in Windows 10 1803 with update KB4493437, Windows 10 1809 with update KB4490481, and Windows 10 1903/1909.

Exclusion routes are defined in the client routing table that are excluded from the VPN tunnel. The real challenge here is determining all the required IP addresses required for Office 365.

Microsoft Published Guidance

Given current events and the heavy demands placed on enterprises supporting exclusively remote workforces, Microsoft has recently published guidance for configuring Always On VPN force tunneling while excluding Office 365 traffic. Their documentation includes all the required IP addresses to configure exclusions for. This will make it much simpler for administrators to configure Always On VPN to support this unique scenario. The following links provide detailed configuration guidance for enabling force tunneling for Always On VPN with exceptions.

Additional Information

Windows 10 Always On VPN Split vs. Force Tunneling

Windows 10 Always On VPN Routing Configuration

Windows 10 Always On VPN Lockdown Mode

Always On VPN Device Tunnel Operation and Best Practices

Always On VPN Device Tunnel Operation and Best PracticesUnlike DirectAccess, Windows 10 Always On VPN settings are deployed to the individual user, not the device. As such, there is no support for logging on without cached credentials using the default configuration. To address this limitation, and to provide feature parity with DirectAccess, Microsoft later introduced the device tunnel option in Windows 10 1709.

Device Tunnel Use Cases

The device tunnel is designed to allow the client device to establish an Always On VPN connection before the user logs on. This enables important scenarios such as logging on without cached credentials. This feature is crucial for organizations who expect users to log on to devices the first time remotely. The device tunnel can also be helpful for remote support, allowing administrators to manage remotely connected Always On VPN clients without having a user logged on. In addition, the device tunnel can alleviate some of the pain caused by administrators resetting remote worker’s passwords, or by users initiating a Self-Service Password Reset (SSPR).

Device Tunnel Requirements

The device tunnel requires Windows 10 Enterprise edition 1709 or later, and the client device must be joined to the domain. The device tunnel must be provisioned in the context of the local system account. Guidance for configuring and deploying a Windows 10 Always On VPN device tunnel can be found here.

Device Tunnel Authentication

The device tunnel is authenticated using a certificate issued to the client device, much the same as DirectAccess does. Authentication takes place on the Routing and Remote Access Service (RRAS) VPN server. It does not require a Network Policy Server (NPS) to perform authentication for the device tunnel.

Always On VPN Device Tunnel Operation and Best Practices

CRL Checking

Eventually an administrator may need to deny access to a device configured with an Always On VPN device tunnel connection. In theory, revoking the client device’s certificate and terminating their IPsec Security Associations (SAs) on the VPN server would accomplish this. However, Windows Server RRAS does not perform certificate revocation checking for Windows 10 Always On VPN device tunnel connections by default. Thankfully an update is available to enable this functionality. See Always On VPN Device Tunnel and Certificate Revocation for more details.

Configuration Best Practices

As the device tunnel is designed only to support domain authentication for remote clients, it should be configured with limited access to the on-premises infrastructure. Below is a list of required and optional infrastructure services that should be reachable over the device tunnel connection.

Required

  • All domain controllers
  • Enterprise DNS servers (if DNS is running on servers other than domain controllers)

Optional

  • All issuing certification authority (CA) servers
  • All certificate services online HTTP responders
  • All certificate services Online Certificate Status Protocol (OCSP) servers
  • System Center Configuration Manager (SCCM) distribution point servers
  • Windows Server Update Services (WSUS) servers
  • Management workstations

Limiting Access

Limiting access over the Always On VPN device tunnel can be accomplished in one of the following two ways.

Traffic Filters

The administrator can configure traffic filters on the device tunnel to restrict access only to those IP addresses required. However, be advised that when a traffic filter is enabled on the device tunnel, all inbound access will be blocked. This effectively prevents any remote management of the device from an on-premises system over the device tunnel.

Host Routes

An alternative to using traffic filters to limit access over the device tunnel is using host routes. Host routes are configured with a /32 prefix size and define a route to a specific individual host. The following is an example of host route configuration in ProfileXML.

Always On VPN Device Tunnel Operation and Best Practices

Note: A PowerShell script that enumerates all enterprise domain controllers and outputs their IP addresses in XML format for use in ProfileXML can be found here.

Caveats

Some organizations may have hundreds or even thousands of domain controllers, so creating individual host route entries for all domain controllers in profileXML may not be practical. In this scenario it is recommended to add host routes only for the domain controllers that belong to the Active Directory site where the VPN server resides.

Supportability

Do not use the <DomainNameInformation> element in ProfileXML or enable force tunneling for the device tunnel. Neither of these configurations are supported.

Tunnel Coexistence

The device tunnel can be safely deployed in conjunction with the user tunnel whenever its functionality is required.

DNS Registration

If the device tunnel and user tunnel are both deployed, it is recommended that only one of the tunnels be configured to register in DNS. If the device tunnel is configured to register its IP address in DNS, be advised that only those devices with routes configured in the device tunnel VPN profile will be able to connect remotely to Always On VPN clients.

Additional Information

Windows 10 Always On VPN Device Tunnel with Azure VPN Gateway

Windows 10 Always On VPN Device Tunnel and Certificate Revocation

Windows 10 Always On VPN Device Tunnel Configuration with Microsoft Intune

Windows 10 Always On VPN Device Tunnel Does Not Connect Automatically

Windows 10 Always On VPN Device Tunnel Missing in Windows 10 UI

Deleting a Windows 10 Always On VPN Device Tunnel

Windows 10 Always On VPN Device Tunnel Configuration using PowerShell

Always On VPN Trusted Network Detection

Always On VPN Trusted Network DetectionWhen deploying Windows 10 Always On VPN, administrators can configure Trusted Network Detection (TND) which enables clients to detect when they are on the internal network. With this option set, the client will only automatically establish a VPN connection when it is outside the trusted network. Trusted network detection can be configured on both device tunnel and user tunnel connections.

TND Operation

When trusted network detection is configured, the VPN client will evaluate the DNS suffix assigned to all physical (non-virtual or tunnel) adapters that are active. If any of them match the administrator-defined trusted network setting, the client is determined to be on the internal network and the VPN connection will not connect. If the DNS suffix is not present on any of these adapters, the client is determined to be outside the internal network and the VPN connection will establish automatically.

TND Configuration

Trusted network detection is defined in the Intune UI or in ProfileXML as a string that matches the DNS suffix assigned to clients on the internal network. In this example, the DNS suffix on the internal network is lab.richardhicks.net.

Always On VPN Trusted Network Detection

Note: Your organization might have more than one DNS suffix. Ensure that the trusted network detection configuration includes all DNS suffixes in use in the environment to ensure reliable operation.

Intune

Follow the steps below to configured trusted network detection in Microsoft Intune.

  1. Open the Intune management portal (https://devicemanagement.microsoft.com/).
  2. Navigate to Devices > Configuration Profiles > [Profile Name] > Properties > Settings.
  3. Click on Trusted Network Detection.
  4. Enter the DNS suffix(es) used on the internal network.

Always On VPN Trusted Network Detection

ProfileXML

To define Trusted Network Detection in ProfileXML, add the TrustedNetworkDetection element as follows.

Always On VPN Trusted Network Detection

Caveats

In some instances, an Always On VPN client connection may persist, even if the client is connected to the internal network. A common scenario is when a client device connects to a Wi-Fi network that is not connected to the corporate network (for example guest Wi-Fi), then connects to the internal network with Ethernet via a docking station. If the Wi-Fi connection is still available, the Always On VPN connection will persist, even though the machine is connected to the internal network. This is expected and by design.

Workaround

To address this specific scenario, administrators can implement changes via group policy to the way Windows handles multiple connections to the same network. For example, beginning with Windows 10 1709, group policy can be configured to ensure that Windows 10 clients prefer wired Ethernet network connections over Wi-Fi, and to ensure that Wi-Fi connections disconnect when an Ethernet connection is detected.

GPO Configuration

Open the Group Policy management console (gpmc.msc) and perform the following steps to create the required group policy objects.

  1. Create a new Group Policy Object (GPO).
  2. Right-click the new GPO and choose Edit.
  3. Expand Computer Configuration > Administrative Templates > Network > Windows Connection Manager.
  4. Double-click the policy Minimize the number of simultaneous connections to the Internet or a Windows Domain.
  5. Select Enabled.
  6. From the Minimize Policy Options drop-down list choose 1 = Minimize simultaneous connections. Optionally you can choose to disable Wi-Fi whenever connected to Ethernet by choosing 3 = Prevent Wi-Fi when on Ethernet.
  7. Click Ok.Always On VPN Trusted Network Detection
  8. Double-click the policy Enable Windows to soft-disconnect a computer from a network.
  9. Select Disabled.
  10. Click Ok.Always On VPN Trusted Network Detection

Additional Information

Understanding and Configuring Windows Connection Manager

Always On VPN Device Tunnel with Azure VPN Gateway

Always On VPN Device Tunnel with Azure VPN GatewayAlways On VPN is infrastructure independent, which allows for many different deployment scenarios including on-premises and cloud-based. In Microsoft Azure, the Azure VPN gateway can be configured to support Windows 10 Always On VPN client connections in some scenarios. Recently I wrote about using the Azure VPN gateway for Always On VPN user tunnels. In this post I’ll describe how to configure the Azure VPN gateway to support an Always On VPN device tunnel.

Limitations

There are a few crucial limitations that come with using the Azure VPN gateway for Always On VPN. Importantly, the Azure VPN gateway can support either user tunnels or device tunnels, not both at the same time. In addition, Azure supports only a single VPN gateway per VNet, so deploying an additional VPN gateway in the same VNet to support Always On VPN user tunnels is not an option.

Root CA Certificate

The Always On VPN device tunnel is authenticated using a machine certificate issued to domain-joined Windows 10 Enterprise edition clients by the organization’s internal Certification Authority (CA). The CA’s root certificate must be uploaded to Azure for the VPN gateway to authorize device tunnel connections. The root CA certificate can be exported using the Certification Authority management console (certsrv.msc) or via the command line.

Export Certificate – GUI

Follow the steps below to export a root CA certificate using the Certification Authority management console.

1. On the root CA server, open the Certification Authority management console.
2. Right-click the CA and choose Properties.
3. Select the CA server’s certificate and choose View Certificate.
4. Select the Details tab and click Copy to File.
5. Click Next.
6. Choose Base-64 encoded X.509 (.CER).

Always On VPN Device Tunnel with Azure VPN Gateway

7. Click Next.
8. Enter a location to save the file to.
9. Click Next, Finish, and Ok.

Export Certificate – Command Line

Follow the steps below to export a root CA certificate using the command line.

1. On the root CA server, open an elevated command window (not a PowerShell window).
2. Enter certutil.exe -ca.cert root_certificate.cer.
3. Enter certutil.exe -encode root.cer root_certificate_base64.cer.

Copy Public Key

1. Open the saved root certificate file using Notepad.
2. Copy the file contents between the BEGIN CERTIFICATE and END CERTIFICATE tags, as shown here. Use caution and don’t copy the carriage return at the end of the string.

Always On VPN Device Tunnel with Azure VPN Gateway

Point-to-Site Configuration

The Azure VPN gateway must be deployed as a Route-Based gateway to support point-to-site VPN connections. Detailed requirements for the gateway can be found here. Once the VPN gateway has been provisioned, follow the steps below to enable point-to-site configuration for Always On VPN device tunnels.

1. In the navigation pane of the Azure VPN gateway settings click Point-to-site configuration.
2. Click the Configure now link and specify an IPv4 address pool to be assigned to VPN clients. This IP address pool must be unique in the organization and must not overlap with an IP address ranges defined in the Azure virtual network.
3. From the Tunnel type drop-down list select IKEv2.
4. In the Root certificates section enter a descriptive name for the certificate in the Name field.
5. Copy and paste the Base64 encoded public key copied previously into the Public certificate data field.
6. Click Save to save the configuration.

Always On VPN Device Tunnel with Azure VPN Gateway

VPN Client Configuration

To support the Always On VPN device tunnel, the client must have a certificate issued by the internal CA with the Client Authentication Enhanced Key Usage (EKU). Detailed guidance for deploying a Windows 10 Always On VPN device tunnel can be found here.

Download VPN Configuration

1. Click Point-to-site configuration.
2. Click Download VPN client.
3. Click Save.
4. Open the downloaded zip file and extract the VpnSettings.xml file from the Generic folder.
5. Copy the FQDN in the VpnServer element in VpnSettings.xml. This is the FQDN that will be used in the template VPN connection and later in ProfileXML.

Create a Test VPN Connection

It is recommended to create a test VPN connection to perform validation testing of the Azure VPN gateway before provisioning an Always On VPN device tunnel broadly. On a domain-joined Windows 10 enterprise client, create a new VPN connection using IKEv2 with machine certificate authentication. Use the VPN server FQDN copied from the VpnSettings.xml file previously.

Always On VPN Device Tunnel with Azure VPN Gateway

Create an Always On VPN Connection

Once the VPN has been validated using the test profile created previously, an Always On VPN profile can be created and deployed using Intune, SCCM, or PowerShell. The following articles can be used for reference.

Deploy Always On VPN device tunnel using PowerShell

Deploy Always On VPN device tunnel using Intune

IKEv2 Security Configuration

The default IKEv2 security parameters used by the Azure VPN gateway are better than Windows Server, but the administrator will notice that a weak Diffie-Hellman (DH) key (Group 2 – 1024 bit) is used during IPsec phase 1 negotiation.

Always On VPN Device Tunnel with Azure VPN Gateway

Use the following PowerShell commands to update the default IKEv2 security parameters to recommended baseline defaults, including 2048-bit keys (DH group 14) and AES-128 for improved performance.

Connect-AzAccount
Select-AzSubscription -SubscriptionName [Azure Subscription Name]

$Gateway = [Gateway Name]
$ResourceGroup = [Resource Group Name]

$IPsecPolicy = New-AzVpnClientIpsecParameter -IpsecEncryption AES128 -IpsecIntegrity SHA256 -SALifeTime 28800 -SADataSize 102400000 -IkeEncryption AES128 -IkeIntegrity SHA256 -DhGroup DHGroup14 -PfsGroup PFS14

Set-AzVpnClientIpsecParameter -VirtualNetworkGatewayName $Gateway -ResourceGroupName $ResourceGroup -VpnClientIPsecParameter $IPsecPolicy

Note: Be sure to update the cryptography settings on the test VPN connection and in ProfileXML for Always On VPN connections to match the new VPN gateway settings. Failing to do so will result in an IPsec policy mismatch error.

Additional Information

Windows 10 Always On VPN User Tunnel with Azure VPN Gateway

Windows 10 Always On VPN IKEv2 Security Configuration

Windows 10 Always On VPN Device Tunnel Configuration using Microsoft Intune

Windows 10 Always On VPN Device Tunnel Configuration using PowerShell

Windows 10 Always On VPN Options for Azure Deployments

Windows 10 Always On VPN IKEv2 Features and Limitations

Always On VPN IKEv2 Policy Mismatch Error

Always On VPN IKEv2 Policy Mismatch ErrorThe Internet Key Exchange version 2 (IKEv2) VPN protocol is the protocol of choice for Windows 10 Always On VPN deployments where the highest levels of security and assurance are required. However, as I’ve written about in the past, often the default IKEv2 security settings are less than desirable. Before using IKEv2 VPN in a production environment the administrator will need to update these security settings accordingly.

Connection Failure

When configuring Windows Server Routing and Remote Access Service (RRAS) or a third-party VPN appliance to support IKEv2 using custom security policies, the administrator may encounter a scenario in which a connection cannot be established due to a policy mismatch error. When the connection attempt fails, an error will be recorded in the Windows Application event log from the RasClient source with Event ID 20227. The error message states the following:

“The user [username] dialed a connection named [connection name] which has failed. The error code returned on failure is 13868.”

Always On VPN IKEv2 Policy Mismatch Error

Error Code 13868

Error code 13868 translates to ERROR_IPSEC_IKE_POLICY_MATCH. Essentially this error indicates that the IKEv2 security policy on the client did not match the configuration on the server.

Server Configuration

To view the current IKEv2 IPsec policy configuration, open an elevated PowerShell command window and run the following command.

Get-VpnServerIPsecConfiguration

Always On VPN IKEv2 Policy Mismatch Error

Client Configuration

To ensure interoperability, the VPN client must be configured to use the same IKEv2 security policy as defined on the sever. To view a VPN client’s currently configured IKEv2 security policy, open an elevated PowerShell command window and run the following command.

Get-VpnConnection -Name [connection name] | Select-Object -ExpandProperty IPsecCustomPolicy

Always On VPN IKEv2 Policy Mismatch Error

Note: If this PowerShell command returns no output, the VPN connection is not using a custom IKEv2 IPsec security policy.

Updating Settings

Guidance for configuring IKEv2 security policies on Windows Server RRAS and Windows 10 can be found here.

NPS Policy

Another common cause of IKEv2 policy mismatch errors is a misconfigured Network Policy Server (NPS) network policy. Specifically, administrators may disable Basic and Strong encryption for MPPE in an attempt to improve security.

Always On VPN IKEv2 Policy Mismatch Error

The NPS policy for Always On VPN must include Strong encryption at a minimum. Basic and No encryption can be safely disabled.

Always On VPN IKEv2 Policy Mismatch Error

Summary

IKEv2 policy mismatch errors can be resolved easily by ensuring both the VPN server and client are configured to use the same IPsec security policies. Use the PowerShell commands in the above referenced above to validate settings and make changes when necessary.

Additional Information

Windows 10 Always On VPN IKEv2 Security Configuration

Windows 10 Always On VPN IKEv2 Features and Limitations

Show-VpnConnectionIPsecConfiguration PowerShell script on Github

Set-IKEv2SecurityBaseline PowerShell script on Github

Always On VPN with Azure Gateway

Always On VPN with Azure GatewayRecently I wrote about VPN server deployment options for Windows 10 Always On VPN in Azure. In that post I indicated the native Azure VPN gateway could be used to support Always On VPN connections using Internet Key Exchange version 2 (IKEv2) and Secure Socket Tunneling Protocol (SSTP). In this post I’ll outline the requirements and configuration steps for implementing this solution.

Requirements

To support Always On VPN, point-to-site VPN connections must be enabled on the Azure VPN gateway. Not all Azure VPN gateways are alike, and point-to-site connections are not supported in all scenarios. For Always On VPN, the Azure VPN gateway must meet the following requirements.

VPN SKU

The Azure VPN gateway SKU must be VpnGw1, VpnGw2, VpnGw3, VpnGw1AZ, VpnGw2AZ, or VpnGw3AZ. The Basic SKU is not supported.

VPN Type

The VPN type must be route-based. Policy-based VPN gateways are not supported for point-to-site VPN connections.

Limitations

Using the Azure VPN gateway for Always On VPN may not be ideal in all scenarios. The following limitations should be considered thoroughly before choosing the Azure VPN gateway for Always On VPN.

Device Tunnel

RADIUS/EAP authentication for user tunnel connections is not supported if the Azure VPN gateway is configured to support device tunnel with machine certificate authentication.

Maximum Connections

A maximum of 250, 500, and 1000 concurrent IKEv2 connections are supported when using the VpnGw1/AZ, VpnGw2/AZ, and VpnGw3/AZ SKUs, respectively (x2 for active/active gateway deployments). In addition, a maximum of 128 concurrent SSTP connections are supported for all VPN gateway SKUs (x2 for active/active gateway deployments).

Always On VPN with Azure Gateway

Reference: https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-about-vpngateways#gwsku

RADIUS Requirements

To support Always On VPN connections, the Azure VPN gateway must be configured to authenticate to a RADIUS server. The RADIUS server must be reachable from the VPN gateway subnet. The RADIUS server can be hosted in Azure or on-premises. Before proceeding, ensure that any network routes, firewall rules, and site-to-site VPN tunnel configuration is in place to allow this communication.

RADIUS Configuration

Guidance for configuring Windows Server NPS for Always On VPN can be found here. The only difference when configuring NPS for use with Azure VPN gateway is the RADIUS client configuration.

Open the NPS management console (nps.msc) and follow the steps below to configure Windows Server NPS to support Always On VPN client connections from the Azure VPN gateway.

1. Expand RADIUS Clients and Servers.
2. Right-click RADIUS Clients and choose New.
3. Enter a descriptive name in the Friendly name field.
4. Enter the Azure VPN gateway subnet using CIDR notation in the Address (IP or DNS) field. The gateway subnet can be found by viewing the properties of the Azure VPN gateway in the Azure portal.
5. Enter the shared secret to be used for RADIUS communication in the Shared secret field.

Always On VPN with Azure Gateway

Azure VPN Gateway Configuration

To begin, provision a Virtual Network Gateway in Azure that meets the requirements outlined above. Guidance for implementing an Azure VPN gateway can be found here. Once complete, follow the steps below to enable support for Always On VPN client connections.

Enable Point-to-Site

Perform the following steps to enable point-to-site VPN connectivity.

1. In the navigation pane of the Azure VPN gateway settings click Point-to-site configuration.
2. Click Configure Now and specify an IPv4 address pool to be assigned to VPN clients. This IP address pool must be unique in the organization and must not overlap with any IP address ranges defined in the Azure virtual network.
3. From the Tunnel type drop-down list select IKEv2 and SSTP (SSL).
4. In the RADIUS authentication field enter the IPv4 address of the RADIUS server. At the time of this writing only a single IPv4 address is supported. If RADIUS redundancy is required, consider creating a load balanced NPS cluster.
5. In the Server secret field enter the RADIUS shared secret.
6. Click Save to save the configuration.

Always On VPN with Azure Gateway

VPN Client Configuration

Perform the following steps to configure a Windows 10 VPN client to connect to the Azure VPN gateway.

Download VPN Configuration

1. Click Point-to-site configuration.
2. Click Download VPN client.
3. Select EAPMSCHAv2 (yes, that’s correct even if EAP-TLS will be used!)
4. Click Download.
5. Open the downloaded zip file and extract the VpnSettings.XML file from the Generic folder.
6. Copy the FQDN in the VpnServer element in VpnSettings.XML. This is the FQDN that will be used in the template VPN connection and later in ProfileXML.

Always On VPN with Azure Gateway

Create a Test VPN Connection

On a Windows 10 device create a test VPN profile using the VPN server address copied previously. Configure EAP settings to match those configured on the NPS server and test connectivity.

Create an Always On VPN Connection

Once the VPN has been validated using the test profile created previously, the VPN server and EAP configuration from the test profile can be used to create the Always On VPN profile for publishing using Intune, SCCM, or PowerShell.

IKEv2 Security Configuration

The default IKEv2 security parameters used by the Azure VPN gateway are better than Windows Server, but the administrator will notice that a weak DH key (1024 bit) is used in phase 1 negotiation.

Always On VPN with Azure Gateway

Use the following PowerShell commands to update the default IKEv2 security parameters to recommended baseline defaults, including 2048-bit keys (DH group 14) and AES-128 for improved performance.

Connect-AzAccount
Select-AzSubscription -SubscriptionName [Azure Subscription Name]

$Gateway = [Gateway Name]
$ResourceGroup = [Resource Group Name]

$IPsecPolicy = New-AzVpnClientIpsecParameter -IpsecEncryption AES128 -IpsecIntegrity SHA256 -SALifeTime 28800 -SADataSize 102400000 -IkeEncryption AES128 -IkeIntegrity SHA256 -DhGroup DHGroup14 -PfsGroup PFS14

Set-AzVpnClientIpsecParameter -VirtualNetworkGatewayName $Gateway -ResourceGroupName $ResourceGroup -VpnClientIPsecParameter $IPsecPolicy

Note: Be sure to update the cryptography settings on the test VPN connection and in ProfileXML for Always On VPN connections to match the new VPN gateway settings. Failing to do so will result in an IPsec policy mismatch error.

Additional Information

Microsoft Azure VPN Gateway Overview

About Microsoft Azure Point-to-Site VPN

Windows 10 Always On VPN IKEv2 Security Configuration

 

 

 

%d bloggers like this: