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

 

 

 

Always On VPN and RRAS with Single NIC

Always On VPN and RRAS with Single NICI’m commonly asked “can Windows Server with Routing and Remote Access Service (RRAS) be configured with a single network interface?” This is likely because the official Microsoft documentation references only a multihomed dual NIC configuration, leading many to believe it is a strict requirement.

Single NIC

Deploying Windows Server RRAS with a single network interface is indeed supported and works without issue. There are no functional limitations imposed by using a single network interface. All features are fully supported in this scenario. The choice to use one or two network interfaces is purely a design choice, driven by several factors such as current network configuration and security requirements.

Dual NIC

Although a single NIC configuration is fully supported, there are some important advantages associated with mulithome dual NIC deployments. The following should be considered when deciding between single NIC and dual NIC VPN configurations.

Traffic Segmentation

Having separate internal and external network connections provides logical and physical separation of trusted and untrusted network traffic. Terminating connections from Always On VPN clients on the Internet in an isolated perimeter or DMZ network yields positive security benefits.

Firewall Configuration

Using two network interfaces allows for a more restrictive Windows Firewall policy to be applied to the external interface. This reduces the exposure of running services on the RRAS server to untrusted networks. This is especially critical if the VPN server is Windows Server RRAS and it is joined to a domain.

Network Performance

For very busy RRAS servers, having two network interfaces can improve network performance. With two network interfaces, network traffic is distributed between two network adapters, reducing utilization on each interface.

Dual NIC Best Practices

When deploying an RRAS server with dual NICs, the following recommendations for network interface configuration should be followed.

IP Addressing

Each network interface must be assigned an IP address from a unique subnet. Having both NICs on the same subnet is not supported.

Default Gateway

The default gateway should be configured on the external facing network interface only. The internal interface should not be configured with a gateway. Rather, static routes to any remote internal networks should be configured.

To add a static route on a Windows Server, open an elevated PowerShell command window and run the following command.

New-NetRoute -AddressFamily IPv4 -DestinationPrefix 10.0.0.0/8 -InterfaceAlias ‘Internal’ -NextHop 172.21.12.254

DNS

For domain-joined RRAS servers, corporate DNS servers should be configured on the Internal network interface only. No DNS servers should be configured on the external interface. If the server is not joined to a domain, DNS servers can be configured on whichever interface has connectivity to the defined DNS servers.

NAT

When the RRAS server is behind a device performing Network Address Translation (NAT), the NAT should be configured to translate only the destination address (DNAT). This allows the VPN server (or load balancer for multiserver deployments) to see the client’s original source IP address, which ensures efficient traffic distribution and meaningful log data.

Client, Service, and Protocol Bindings

All unnecessary clients, services, and protocols should be unbound from the external network interface. It is recommended that only the IPv4 and IPv6 protocols be enabled on the external interface, as shown here. Again, this reduces exposure for the server to the untrusted external network.

Always On VPN and RRAS with Single NIC

Summary

The dual NIC, multihomed configuration is generally recommended for most deployments as it offers security and performance advantages over the single NIC configuration. For organizations with less demanding security requirements, a single NIC deployment can be deployed safely without compromising functionality or supportability. In addition, a single NIC deployment may be the best option when multiple networks aren’t readily available.

Additional Information

Windows 10 Always On VPN and Windows Server Routing and Remote Access (RRAS)

Windows 10 Always On VPN Protocol Recommendations for Windows Server RRAS

Windows 10 Always On VPN Options for Azure Deployments

Windows 10 Always On VPN Hands On Training

Error Importing Windows Server RRAS Configuration

Error Importing Windows Server RRAS Configuration Windows Server and the Routing and Remote Access Service (RRAS) is a popular choice for Windows 10 Always On VPN deployments. It is easy to implement and support, offers flexible scalability, and is cost-effective. In addition, it provides support for a TLS-based VPN protocol which is required for many deployments.

Configuration Backup

When deploying RRAS to support Always On VPN, it’s an excellent idea to export the configuration once all settings have been finalized. Often this is done by opening an elevated command window and running netsh.exe ras dump and piping the output to a text file, as shown here.

netsh.exe ras dump > rasconfig.txt

Import Error

Importing a saved configuration is accomplished by opening an elevated command window and running netsh.exe exec [filename], as shown here.

netsh.exe exec rasconfig.txt

Oddly, this doesn’t work by default. The import will fail and return the following error message.

“The following command was not found: ■.”

Error Importing Windows Server RRAS Configuration

Root Cause

Importing the RRAS configuration fails because the default configuration output is saved in Unicode format. Inexplicably this encoding is not recognized by netsh.exe when importing the configuration.

Workaround

Follow the steps below to save the configuration file in a format that can be imported using netsh.exe.

1. Open the exported configuration file using notepad.exe.
2. From the Menu bar choose File > Save As.
3. From the Encoding drop-down list choose ANSI.
4. Click Save.

Error Importing Windows Server RRAS Configuration

Once complete, import the file using netsh.exe exec [filename]. Restart the RemoteAccess service to apply the changes.

PowerShell

Administrators can use PowerShell to export the RRAS configuration and ensure the correct encoding format is used by default. To do this, open an elevated PowerShell window and run the following command.

Invoke-Command -ScriptBlock {netsh ras dump} | Out-File [filename] -Encoding ASCII

Additional Information

Windows 10 Always On VPN and Windows Server Routing and Remote Access Service (RRAS)

Windows 10 Always On VPN Protocol Recommendations for Windows Server Routing and Remote Access Service (RRAS)

Always On VPN RasMan Errors in Windows 10 1903

Always On VPN RasMan Errors in Windows 10 1903After deploying or upgrading to Windows 10 1903, administrators may find that Windows 10 Always On VPN connections fail to establish successfully. Always On VPN connections continue to work for Windows 10 1809 and earlier clients, however.

Important Note: The issue described in this article has been addressed in KB4505903 (build 18362.267) released July 26, 2019.

RasMan Event Log Errors

When this occurs, the application event log contains an error with Event ID 1000 that includes the following information.

“Faulting application name: svchost.exe_RasMan…”, “Faulting module name: rasmans.dll”, and “Exception code: 0xc0000005”

Always On VPN RasMan Errors in Windows 10 1903 Administrators may find that Windows 10 Always On VPN connections fail after deploying or upgrading to Windows 10 1903. Always On VPN connections continue to work for Windows 10 1809 and earlier clients. RasMan Event Log Errors When this occurs, the application event log contains an error with Event ID 1000 that includes the following information. “Faulting application name: svchost.exe_RasMan…”, “Faulting module name: rasmans.dll”, and “Exception code: 0xc0000005” Root Cause RasMan failures can occur in Windows 10 1903 clients when telemetry is disabled via group policy or the registry. Microsoft has identified the issue and is currently working on a fix. Workaround As a temporary workaround to restore Always On VPN connectivity, enable telemetry on Windows 10 1903 using Active Directory or local group policy, the local registry, or PowerShell. Group Policy Create a new GPO or edit an existing one by opening the group policy management console (gpmc.msc) and performing the following steps. 1. Expand Computer Configuration > Administrative Templates > Windows Components > Data Collection and Preview Builds 2. Double-Click Allow Telemetry. 3. Select Enabled. 4. Choose 1-Basic, 2-Enhanced, or 3-Full (do not select 0-Security). 5. Click Ok. Registry Telemetry can also be enabled locally by opening the registry editor (regedit.exe) and modifying the following registry setting. HKLM\SOFTWARE\Policies\Microsoft\Windows\DataCollection\AllowTelemetry DWORD = 1 Note: The AllowTelemetry value can be removed entirely, if desired. PowerShell PowerShell can also be used modify or remove the AllowTelemetry value on Windows 10 1903 clients. Run the following PowerShell command to update the AllowTelemetry setting. New-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\' -Name AllowTelemetry -PropertyType DWORD -Value 1 -Force Optionally, run the following PowerShell command to remove the AllowTelemetry setting entirely. Remove-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\' -Name AllowTelemetry Restart Required Once these changes have been made, restart the client and test the Always On VPN connection. Additional Information asdf

Root Cause

RasMan failures can occur in Windows 10 1903 clients when telemetry is disabled via group policy or the registry. Microsoft has identified the issue and is currently working on a fix.

Workaround

As a temporary workaround to restore Always On VPN connectivity, enable telemetry on Windows 10 1903 using Active Directory or local group policy, the local registry, or PowerShell.

Group Policy

Create a new GPO or edit an existing one by opening the group policy management console (gpmc.msc) and performing the following steps.

1. Expand Computer Configuration > Administrative Templates > Windows Components > Data Collection and Preview Builds
2. Double-click Allow Telemetry.
3. Select Enabled.
4. Choose 1-Basic, 2-Enhanced, or 3-Full (do not select 0-Security).
5. Click Ok.

Always On VPN RasMan Errors in Windows 10 1903 Administrators may find that Windows 10 Always On VPN connections fail after deploying or upgrading to Windows 10 1903. Always On VPN connections continue to work for Windows 10 1809 and earlier clients. RasMan Event Log Errors When this occurs, the application event log contains an error with Event ID 1000 that includes the following information. “Faulting application name: svchost.exe_RasMan…”, “Faulting module name: rasmans.dll”, and “Exception code: 0xc0000005” Root Cause RasMan failures can occur in Windows 10 1903 clients when telemetry is disabled via group policy or the registry. Microsoft has identified the issue and is currently working on a fix. Workaround As a temporary workaround to restore Always On VPN connectivity, enable telemetry on Windows 10 1903 using Active Directory or local group policy, the local registry, or PowerShell. Group Policy Create a new GPO or edit an existing one by opening the group policy management console (gpmc.msc) and performing the following steps. 1. Expand Computer Configuration > Administrative Templates > Windows Components > Data Collection and Preview Builds 2. Double-Click Allow Telemetry. 3. Select Enabled. 4. Choose 1-Basic, 2-Enhanced, or 3-Full (do not select 0-Security). 5. Click Ok. Registry Telemetry can also be enabled locally by opening the registry editor (regedit.exe) and modifying the following registry setting. HKLM\SOFTWARE\Policies\Microsoft\Windows\DataCollection\AllowTelemetry DWORD = 1 Note: The AllowTelemetry value can be removed entirely, if desired. PowerShell PowerShell can also be used modify or remove the AllowTelemetry value on Windows 10 1903 clients. Run the following PowerShell command to update the AllowTelemetry setting. New-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\' -Name AllowTelemetry -PropertyType DWORD -Value 1 -Force Optionally, run the following PowerShell command to remove the AllowTelemetry setting entirely. Remove-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\' -Name AllowTelemetry Restart Required Once these changes have been made, restart the client and test the Always On VPN connection. Additional Information asdf

Registry

Telemetry can also be enabled locally by opening the registry editor (regedit.exe) and modifying the following registry setting.

HKLM\SOFTWARE\Policies\Microsoft\Windows\DataCollection\AllowTelemetry DWORD = 1

Always On VPN RasMan Errors in Windows 10 1903 Administrators may find that Windows 10 Always On VPN connections fail after deploying or upgrading to Windows 10 1903. Always On VPN connections continue to work for Windows 10 1809 and earlier clients. RasMan Event Log Errors When this occurs, the application event log contains an error with Event ID 1000 that includes the following information. “Faulting application name: svchost.exe_RasMan…”, “Faulting module name: rasmans.dll”, and “Exception code: 0xc0000005” Root Cause RasMan failures can occur in Windows 10 1903 clients when telemetry is disabled via group policy or the registry. Microsoft has identified the issue and is currently working on a fix. Workaround As a temporary workaround to restore Always On VPN connectivity, enable telemetry on Windows 10 1903 using Active Directory or local group policy, the local registry, or PowerShell. Group Policy Create a new GPO or edit an existing one by opening the group policy management console (gpmc.msc) and performing the following steps. 1. Expand Computer Configuration > Administrative Templates > Windows Components > Data Collection and Preview Builds 2. Double-Click Allow Telemetry. 3. Select Enabled. 4. Choose 1-Basic, 2-Enhanced, or 3-Full (do not select 0-Security). 5. Click Ok. Registry Telemetry can also be enabled locally by opening the registry editor (regedit.exe) and modifying the following registry setting. HKLM\SOFTWARE\Policies\Microsoft\Windows\DataCollection\AllowTelemetry DWORD = 1 Note: The AllowTelemetry value can be removed entirely, if desired. PowerShell PowerShell can also be used modify or remove the AllowTelemetry value on Windows 10 1903 clients. Run the following PowerShell command to update the AllowTelemetry setting. New-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\' -Name AllowTelemetry -PropertyType DWORD -Value 1 -Force Optionally, run the following PowerShell command to remove the AllowTelemetry setting entirely. Remove-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\' -Name AllowTelemetry Restart Required Once these changes have been made, restart the client and test the Always On VPN connection. Additional Information asdf

Note: The AllowTelemetry value can be removed entirely, if desired.

PowerShell

PowerShell can also be used modify or remove the AllowTelemetry value on Windows 10 1903 clients. Run the following PowerShell command to update the AllowTelemetry setting.

New-ItemProperty -Path ‘HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\’ -Name AllowTelemetry -PropertyType DWORD -Value 1 -Force

Optionally, run the following PowerShell command to remove the AllowTelemetry setting entirely.

Remove-ItemProperty -Path ‘HKLM:\SOFTWARE\Policies\Microsoft\Windows\DataCollection\’ -Name AllowTelemetry

Service Restart Required

Once these changes have been made, restart the Remote Access Connection Manager service (RasMan) using the Services mnagement console (services.msc) or by running the following PowerShell command.

Restart-Service RasMan -PassThru

Optionally, the client can be rebooted to apply these changes.

Additional Information

Windows 10 1903 Known Issues

 

Always On VPN LockDown Mode

Always On VPN LockDown ModeWhen an Always On VPN connection is provisioned to a Windows 10 client, there’s nothing to prevent a user from disconnecting or even deleting the connection. Some administrators have expressed concern about this, fearful that users may disable the VPN to improve performance or circumvent access controls when force tunneling is enabled. Also, administrators may wish to prevent users from accidentally or purposefully making changes to the configuration, or even deleting the connection entirely.

LockDown Mode

To address these concerns, Microsoft included a feature called LockDown mode for Always On VPN. Once enabled, the following conditions apply.

  • The LockDown VPN connection is always on.
  • The LockDown VPN connection cannot be disabled.
  • The user can’t make changes to or delete the LockDown connection.
  • No other VPN connections can exist on the client.
  • Force tunneling is enabled by default (split tunneling in LockDown mode is not supported).

Challenges with LockDown Mode

Always On VPN LockDown mode brings with it some unique challenges, however. Consider the following.

Limited Protocol Support

LockDown mode only supports IKEv2 and the native (built-in) VPN client. Third-party plug-in provider clients are not supported. IKEv2 is an excellent VPN protocol in terms of security, but operationally speaking it has some serious drawbacks.

Force Tunneling Only

LockDown mode uses force tunneling exclusively. All network traffic must go over the VPN connection. However, if the VPN connection is not available, the client will be unable to access any network resources at all, local or remote.

Captive Portal Issues

LockDown mode prevents clients from connecting to network resources from a network with a captive portal.

On-premises Connectivity

In LockDown mode all network traffic must flow over the VPN tunnel even if the client is on the internal network. This also means that if the VPN server is not reachable internally (unable to resolve public hostname, protocols/ports blocked by internal firewall, unable to route to VPN server, etc.) the client will not be able to access any internal or external network resources at all.

Deleting a LockDown VPN Connection

Deleting a LockDown VPN connection is also challenging. Administrators will find that trying to delete it using the UI or PowerShell often fails. To delete a LockDown Always On VPN connection, use psexec.exe to open an elevated PowerShell command window running in the system context using the following command.

.\psexec.exe -i -s C:\windows\system32\WindowsPowerShell\v1.0\powershell.exe

In the new elevated PowerShell window run the following commands to delete the LockDown VPN connection.

$Namespace = “root\cimv2\mdm\dmmap”
$ClassName = “MDM_VPNv2_01”

$obj = Get-CimInstance -Namespace $Namespace -ClassName $ClassName
Remove-CimInstance -CimInstance $obj

Optionally, download and run Remove-LockDownVPN.ps1 here.

Summary

While Always On VPN LockDown mode might seem like a good idea initially, its implementation is heavy-handed and practically speaking ends up causing more problems than it solves. For administrators that plan to enable this feature, carefully consider the drawbacks and limitations outlined above and their impact on supportability and the user experience.

Additional Information

Windows Always On VPN Device Tunnel Config using Microsoft Intune

Windows 10 Always On VPN Security Configuration 

Windows 10 Always On VPN Hands-On Training

 

Always On VPN IKEv2 Security Configuration

Always On VPN IKEv2 Security ConfigurationWhen deploying Windows 10 Always On VPN, many administrators choose the Internet Key Exchange version 2 (IKEv2) protocol to provide the highest level of security and protection for remote connections. However, many do not realize the default security parameters for IKEv2 negotiated between a Windows Server running the Routing and Remote Access Service (RRAS) and a Windows 10 VPN client are far less than ideal from a security perspective. Additional configuration on both the server and the client will be required to ensure adequate security and protection for IKEv2 VPN connections.

Windows 10 and RRAS IKEv2 Defaults

In their default configuration, a Windows 10 client connecting to a Windows Server running RRAS will negotiate an IKEv2 VPN connection using the following IPsec security parameters.

  • Encryption: 3DES
  • Authentication/Integrity: SHA-1
  • Key Size: DH Group 2 (1024 bit)

This information can be obtained by opening an elevated PowerShell command window and running the following command.

Get-NetIPsecMainModeSA | Select-Object -First 1

Always On VPN IKEv2 Security Configuration

This can also be confirmed by viewing a network trace as shown here.

Always On VPN IKEv2 Security Configuration

These IPsec security parameters might have been acceptable in the 90’s, but they certainly are not today. 🙂

Improving IKEv2 Security

To provide a baseline level of protection to meet today’s requirements for security and privacy for IKEv2 VPN connections, the following are the minimum recommended IPsec security parameters.

  • Encryption: AES128
  • Authentication/Integrity: SHA-256
  • Key Size: DH Group 14 (2048 bit)

RRAS Custom IPsec Policy

To implement these recommended security baselines for IKEv2 on a Windows Server running RRAS it will be necessary to define a custom IPsec security policy. To do this, open an elevated PowerShell command window and run the following commands on each RRAS server.

Set-VpnServerConfiguration -CustomPolicy -AuthenticationTransformConstants SHA256128 -CipherTransformConstants AES128 -DHGroup Group14 -EncryptionMethod AES128 -IntegrityCheckMethod SHA256 -PFSgroup PFS2048 -SADataSizeForRenegotiationKilobytes 102400

Restart the Remote Access Management service for the changes to take effect.

Restart-Service RemoteAccess -PassThru

Always On VPN IKEv2 Security Configuration

Note: A PowerShell script to implement the custom IPsec security policy settings shown above can be downloaded here.

Windows 10 Client Settings

The IPsec policy must match on both the server and the client for an IKEv2 VPN connection to be successful. Unfortunately, none of the IKEv2 IPsec security association parameters proposed by default on Windows 10 clients use 2048-bit keys (DH Group 14), so it will be necessary to define a custom IPsec security policy on the client to match the settings configured on the server.

To configure a matching IPsec security policy on an individual Windows 10 VPN client, open an elevated PowerShell command window and run the following command.

$connection = “[connection name]”
Set-VpnConnectionIPsecConfiguration -ConnectionName $connection -AuthenticationTransformConstants SHA256128 -CipherTransformConstants AES128 -DHGroup Group14 -EncryptionMethod AES128 -IntegrityCheckMethod SHA256 -PFSgroup PFS2048 -Force

Always On VPN IKEv2 Security Configuration

Restore Defaults

In the process of testing it may be necessary to restore the default IKEv2 configuration on both the client and the server. This can be accomplished by running the following PowerShell commands.

Server – Set-VpnServerConfiguration -RevertToDefault

Client – Set-VpnConnectionIPsecConfiguration -ConnectionName [connection_name] -RevertToDefault -Force

Always On VPN XML Settings

To implement a custom IPsec policy using the minimum recommended security settings for an Always On VPN connection using IKEv2, add the following settings to your ProfileXML.

<VPNProfile>
 <NativeProfile>
  <CryptographySuite>
   <AuthenticationTransformConstants>SHA256128</AuthenticationTransformConstants>
   <CipherTransformConstants>AES128</CipherTransformConstants>
   <EncryptionMethod>AES128</EncryptionMethod>
   <IntegrityCheckMethod>SHA256</IntegrityCheckMethod>
   <DHGroup>Group14</DHGroup>
   <PfsGroup>PFS2048</PfsGroup>
  </CryptographySuite>
 </NativeProfile>
</VPNProfile>

Why Not AES 256?

In the examples above you’ll notice that I’ve chosen to use AES128 and not AES256. This is by design, as AES256 does not provide any practical additional security in most use cases. Details here.

Enhanced Security and Performance

To further improve security and performance for IKEv2, consider implementing Elliptic Curve Cryptography (EC) certificates and using Galois Counter Mode (GCM) cipher suites such as GCMAES128 for authentication and encryption.

Additional Information

Always On VPN Certificate Requirements for IKEv2

Always On VPN IKEv2 Connection Failure Error Code 800

Always On VPN IKEv2 Load Balancing with the KEMP LoadMaster Load Balancer

 

%d bloggers like this: