Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Always On VPN SSTP Load Balancing with Citrix NetScaler ADCThe Internet Key Exchange version 2 (IKEv2) VPN protocol is the protocol of choice when the highest level of security is required for Always On VPN connections. It uses IPsec and features configurable security parameters that allow administrators to adjust policies to meet their specific security requirements. IKEv2 is not without some important limitations, but organizations may insist on the use of IKEv2 to provide the greatest protection possible for remote connected clients. Due to complexities of the IKEv2 transport, special configuration on the Citrix ADC is required when load balancing this workload.

Special Note: In December 2019 a serious security vulnerability was discovered on the Citrix ADC that gives an unauthenticated attacker the ability to arbitrarily execute code on the appliance. As of this writing a fix is not available (due end of January 2020) but a temporary workaround can be found here.

Load Balancing IKEv2

When an Always On VPN client establishes a connection using IKEv2, communication begins on UDP port 500, but switches to UDP port 4500 if Network Address Translation (NAT) is detected in the communication path between the client and the server. Because UDP is connectionless, custom configuration is required to ensure that VPN clients maintain connectivity to the same backend VPN server during this transition.

Initial Configuration

Load balancing IKEv2 using the Citrix ADC is similar to other workloads. Below are specific settings and parameters required to load balance IKEv2 using the Citrix ADC.

Note: This article is not a comprehensive configuration guide for the Citrix ADC. It assumes the administrator is familiar with basic load balancing concepts and has experience configuring the Citrix ADC.

Service Settings

The load balancing services for IKEv2 VPN will use UDP ports 500 and 4500. Create the service group and assign group members for UDP 500 as follows.

Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Repeat the steps above to create the service group for UDP port 4500.

Virtual Server Settings

Two virtual servers are required, one for UDP port 500 and one for UDP port 4500. Ensure that the service group using UDP port 500 is bound to the virtual server using the same port.

Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Repeat the steps above to create the virtual service for UDP port 4500.

Service Monitoring

Since IKEv2 uses the UDP protocol, the only option for service monitoring is to use PING, which is configured by default. Ensure that the firewall on the VPN server allows inbound ICMPv4 and ICMPv6 Echo Request. The default PING monitor on the Citrix ADC will ping the resource every 5 seconds. If a different interval is required, the administrator can edit the PING monitor and bind that to the service or service group as necessary.

Persistency Group

A Persistency Group on the Citrix ADC will be configured to ensure that IKEv2 VPN client requests from the same client are always routed to the same backend server. Follow the steps below to create a Persistency Group and assign it to both IKEv2 virtual servers created previously.

1. In the Citrix ADC management console expand Traffic Management > Load Balancing > Persistency Groups.
2. Click Add.
3. Enter a descriptive name for the Persistency Group.
4. Select SOURCEIP from the Persistence drop-down list.
5. Next to the Virtual Server Name section click the Add button.
6. Add both previously configured IKEv2 virtual servers for UDP 500 and 4500.
7. Click Create.

Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Additional Information

Windows 10 Always On VPN SSTP Load Balancing with Citrix NetScaler ADC

Windows 10 Always On VPN IKEv2 Features and Limitations

Windows 10 AlWAYS On VPN and IKEv2 Fragmentation

Windows 10 Always On VPN IKEv2 Security Configuration

Windows 10 Always On VPN Certificate Requirements for IKEv2

Always On VPN SSTP Load Balancing with Citrix NetScaler ADC

Always On VPN SSTP Load Balancing with Citrix NetScaler ADCOne of the many advantages of using Windows Server Routing and Remote Access Service (RRAS) as the VPN server to support Windows 10 Always On VPN connections is that it includes support for the Secure Socket Tunneling Protocol (SSTP). SSTP is a TLS-based VPN protocol that is easy to configure and deploy and is very firewall friendly. This ensures consistent and reliable connectivity even behind restrictive firewalls. The Citrix Application Delivery Controller (ADC), formerly known as NetScaler, is a popular platform for load balancing Always On VPN connections. In this article I’ll describe how to configure load balancing on the Citrix ADC for RRAS VPN connections using the SSTP VPN protocol.

Special Note: In December 2019 a serious security vulnerability was discovered on the Citrix ADC that gives an unauthenticated attacker the ability to arbitrarily execute code on the appliance. As of this writing a fix is not available (due end of January 2020) but a temporary workaround can be found here.

Load Balancing SSTP

Previously I’ve written about some of the use cases and benefits of SSTP load balancing as well as the options for offloading TLS for SSTP VPN connections. Load balancing SSTP eliminates single points of failure and enables support for multiple RRAS VPN servers to increase scalability. It is generally recommended that the Citrix ADC be configured to pass through encrypted SSTP VPN connections. However, TLS offloading can be configured to improve performance and reduce resource utilization on VPN servers, if required.

Configuration

Load balancing SSTP on the Citrix ADC is straightforward and not unlike load balancing a common HTTPS web server. Below are specific settings and parameters required to load balance SSTP using the Citrix ADC.

Note: This article is not a comprehensive configuration guide for the Citrix ADC. It assumes the administrator is familiar with basic load balancing concepts and has experience configuring the Citrix ADC.

Service Settings

The load balancing service for SSTP VPN should be configured to use TCP port 443 and the SSL_BRIDGE protocol. If TLS offload is required, TCP port 80 and the HTTP protocol can be configured. Additional configuration is required on the RRAS server when TLS offload is enabled, however. Detailed information for configuring RRAS and SSTP for TLS offload can be found here.

Always On VPN SSTP Load Balancing with Citrix NetScaler ADC

Virtual Server Settings

The virtual server is configured to use TCP port 443. It is recommended to use SSLSESSION persistence.

Always On VPN SSTP Load Balancing with Citrix NetScaler ADC

The LEASTCONNECTION load balancing method is the recommend option for load balancing method.

Always On VPN SSTP Load Balancing with Citrix NetScaler ADC

Service Monitoring

Using the default TCP monitor (tcp-default) is not recommended for monitoring SSTP, as a simple TCP port check does not accurately reflect the health of the SSTP service running on the RRAS server. To more precisely monitor the SSTP service status, a new custom monitor must be created and bound to the load balancing services. Follow the steps below to configure a custom SSTP VPN monitor on the Citrix ADC.

  1. Open the Citrix ADC management console and expand Traffic Management.
  2. Select Monitors.
  3. Click Add.
  4. Enter a descriptive name in the Name field.
  5. Select HTTP form the Type drop-down list and click Select.
  6. Adjust the Interval and Response Time-out values according to your requirements.
  7. Enter 401 in the Response Codes field and click the “+” button.
  8. In the Response Codes field click the “x” next to 200.
  9. In the HTTP Request field enter HEAD /sra_{BA195980-CD49-458b-9E23-C84EE0ADCD75}/.
  10. Check the box next to Secure (not required if TLS offload is enabled).
  11. Select ns_default_ssl_profile_backend from the SSL profile drop-down list (not required if TLS offload is enabled).
  12. Click Create.

Always On VPN SSTP Load Balancing with Citrix NetScaler ADC

Once complete, bind the new service monitor to the load balancing services or service groups accordingly.

TLS Offload

It is generally recommended that TLS offload not be enabled for SSTP VPN. However, if TLS offload is desired, it is configured in much the same way as a common HTTPS web server. Specific guidance for enabling TLS offload on the Citrix ADC can be found here. Details for configuring RRAS and SSTP to support TLS offload can be found here.

Certificates

When enabling TLS offload for SSTP VPN connections it is recommended that the public SSL certificate be installed on the RRAS server, even though TLS processing will be handled on the Citrix ADC and HTTP will be used between the Citrix ADC and the RRAS server. If installing the public SSL certificate on the RRAS server is not an option, additional configuration will be required. Specifically, TLS offload for SSTP must be configured using the Enable-SSTPOffload.ps1 PowerShell script, which can be found here.

Once the script has been downloaded, open an elevated PowerShell command window and enter the following command.

.\Enable-SSTPOffload.ps1 -CertificateHash [SHA256 Certificate Hash of Public SSL Certificate] -Restart

Example:

.\Enable-SSTPOffload.ps1 -CertificateHash ‘C3AB8FF13720E8AD9047DD39466B3C8974E592C2FA383D4A3960714CAEF0C4F2’ -Restart

Re-Encryption

When offloading TLS for SSTP VPN connections, all traffic between the Citrix ADC and the RRAS server will be sent in the clear using HTTP. In some instances, TLS offload is required only for traffic inspection, not performance gain. In this scenario the Citrix ADC will be configured to terminate and then re-encrypt connections to the RRAS server. When terminating TLS on the Citrix ADC and re-encrypting connections to the RRAS server is required, the same certificate must be used on both the Citrix ADC and the RRAS server. Using different certificates on the RRAS server and the load balancer is not supported.

Additional Information

Windows 10 Always On VPN Load Balancing and SSL Offload

SSL Offload Configuration for Citrix ADC (NetScaler)

Windows 10 Always On VPN SSTP Load Balancing with Kemp LoadMaster

Windows 10 Always On VPN SSTP Load Balancing with F5 BIG-IP

Windows 10 Always On VPN Connects then Disconnects

Windows 10 Always On VPN SSL Certificate Requirements for SSTP

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 Hands On Training in 2020

The calendar of events for our Windows 10 Always On VPN hands-on training classes is now available!

2020 Training Calendar

This year we will be making the following stops.

  • March 3-5 – Denver, CO
  • April 14-16 – New York, NY
  • June 15-15 – Bern, Switzerland (hosted by RealStuff – register here!)
  • August 18-20 – Honolulu, HI
  • October 6-8 – Washington D.C.
  • December 1-3 – San Diego, CA

Always On VPN Hands-On Training

Comprehensive Training

My Windows 10 Always On VPN hands-on training classes will cover all aspects of designing, implementing, and supporting an Always On VPN solution in the enterprise. This three-day course will cover topics such as…

  • Windows 10 Always On VPN overview
  • Introduction to CSP
  • Infrastructure requirements
  • Planning and design considerations
  • Installation, configuration, and client provisioning

Advanced topics will include…

  • Redundancy and high availability
  • Cloud-based deployments
  • Third-party VPN infrastructure and client support
  • Multifactor authentication
  • Always On VPN migration strategies

Windows 10 Always On VPN Hands-On Training Classes for 2018

Register Today

Space is limited, so register now to reserve your spot in one of our Always On VPN hands-on training classes. Hope to see you there!

Always On VPN Hands-On Training

Always On VPN Error Code 858

Always On VPN Error Code 858When configuring Windows 10 Always On VPN using Extensible Authentication Protocol (EAP), the administrator may encounter a scenario in which the client connection fails. The event log will include an event ID 20227 from the RasClient source that includes the following error message.

“The user [domain\username] dialed a connection named [connection name] which has failed. The error code returned on failure is 858.”

Always On VPN Error Code 858

RasClient Error 858

RasClient error code 858 translates to ERROR_EAP_SERVER_CERT_EXPIRED. Intuitively, this indicates that the Server Authentication certificate installed on the Network Policy Server (NPS) has expired. To resolve this issue, renew the certificate on the NPS server.

Additional Information

Windows 10 Always On VPN Network Policy Server (NPS) Load Balancing

Windows 10 Always On VPN and Windows Server 2019 NPS Bug

Windows 10 Always On VPN Error Code 864

Microsoft Intune NDES Connector Error 0x80004003

Microsoft Intune NDES Connector Error 0x80004003To support certificate deployment for non-domain Windows 10 Always On VPN clients, a Windows Server with the Network Device Enrollment Service (NDES) role can be provisioned on-premises. In addition, the Microsoft Intune Connector must be installed and configured on the NDES server to allow Intune-managed clients to request and receive certificates from the on-premises Certification Authority (CA) server.

Connection Status Error

After installing the Microsoft Intune Connector, the administrator may encounter the following error message.

“An error occurred while connecting to the Intune Service. Error code is 0x80004003. The NDES Connector will retry the connection as soon as possible.”

 Microsoft Intune NDES Connector Error 0x80004003

IE Enhanced Security Configuration

This error can occur if Internet Explorer Enhanced Security Configuration (ESC) is enabled. To resolve this issue, disable ESC for administrators and users by opening the Server Manager on the NDES server and performing the following steps.

1. In the navigation pane click Local Server.
2. Click the On link next to IE Enhanced Security Configuration.
3. Click Off in the Administrators section.
4. Click Off in the Users section
5. Click Ok.

Microsoft Intune NDES Connector Error 0x80004003

Once complete, restart the NDES Connector service using the following PowerShell command.

Restart-Service NDESConnectorSvc -PassThru

Additional Configuration

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Microsoft Intune NDES Connector Setup Wizard Ended PrematurelyA Windows Server with the Network Device Enrollment Service (NDES) role can be provisioned on-premises to support certificate deployment for non-domain Windows 10 Always On VPN clients. In addition, the Microsoft Intune Connector must be installed and configured on the NDES server to allow Intune-managed clients to request and receive certificates from the on-premises Certification Authority (CA) server.

Setup Wizard Ended Prematurely

When installing the Microsoft Intune Connector, the administrator may encounter a scenario where the setup wizard fails with the following error message.

“Microsoft Intune Connector Setup Wizard ended prematurely because of an error. Your system has not been modified. To install this program at a later time, run Setup Wizard again. Click the Finish button to exit the Setup Wizard.”

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Cryptographic Service Provider

This error can occur if the NDES server certificate template is configured to use the Key Storage Provider cryptography service provider (CSP). When configuring the certificate template for the NDES server, the Legacy Cryptography Service Provider must be used, as shown here.

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Additional Information

Deploying Windows 10 Always On VPN with Intune using Custom ProfileXML

Windows 10 Always On VPN Device Tunnel Configuration using Microsoft Intune

Deploying Windows 10 Always On VPN with Microsoft Intune

 

Troubleshooting Always On VPN Error Code 864

When configuring an Always On VPN connection, the administrator may encounter a scenario in which a VPN connection fails using either Internet Key Exchange version 2 (IKEv2) or Secure Socket Tunneling Protocol (SSTP). On the Windows 10 client the error message states the following.

“Can’t connect to [connection name]. The remote access connection completed, but authentication failed because a certificate that validates the server certificate was not found in the Trusted Root Certification Authorities certificate store.”

Troubleshooting Always On VPN Error Code 864

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

“The user [username] dialed a connection name [connection name] which has failed. The error code returned on failure is 864.”

Troubleshooting Always On VPN Error Code 864

NPS Server Certificate

Error code 864 is commonly caused by a missing or invalid server certificate on the Network Policy Server (NPS) performing authentication for VPN clients. The NPS server must have a certificate installed in its local computer certificate store from a trusted certification authority (CA) that includes the following.

Subject Name

The subject name must match the hostname defined in the EAP configuration for VPN clients. This may be the NPS server’s hostname but could also be an alias when NPS load balancing is configured.

Troubleshooting Always On VPN Error Code 864

Enhanced Key Usage

The NPS server certificate must include the Server Authentication Enhanced Key Usage (EKU).

Troubleshooting Always On VPN Error Code 864

NPS Policy Configuration

The NPS server certificate must also be selected in the network policy used for VPN client authentication. To confirm correct certificate configuration, open the properties for the Always On VPN network policy and follow the steps below.

1. Select the Constraints tab.
2. Highlight Authentication Methods.
3. Highlight Microsoft: Protected EAP (PEAP) in the EAP Types field.
4. Click Edit.
5. Select the NPS server certificate from the Certificate issued to drop-down list.

Troubleshooting Always On VPN Error Code 864

Ensure the NPS server certificate is also used for client certificate authentication by performing the following steps.

1. Highlight Smart Card or other certificate.
2. Click Edit.
3. Select the NPS server certificate from the Certificate issued to drop-down list.
4. Click Ok.

Troubleshooting Always On VPN Error Code 864

Additional Information

Windows 10 Always On VPN Network Policy Server (NPS) Load Balancing

Always On VPN and RRAS in Azure

Always On VPN and RRAS in AzureWhen deploying Windows 10 Always On VPN, it may be desirable to host the VPN server in Microsoft’s Azure public cloud. Recently I wrote about Always On VPN deployment options in Azure, and in that post I indicated that deploying Windows Server and the Routing and Remote Access Service (RRAS) was one of those options. Although not formally supported by Microsoft, RRAS is often deployed in Azure because it is cost-effective, easy to manage, and provides flexible scalability.

Supportability

It’s important to state once again that although it is possible to successfully deploy Windows Server with RRAS in Azure to support Always On VPN, as of this writing it is not a formally supported workload. If the administrator makes the decision to deploy RRAS in Azure, they must also accept that Microsoft may refuse to assist with troubleshooting in this specific deployment scenario.

Always On VPN and RRAS in Azure

Reference: https://support.microsoft.com/en-us/help/2721672/microsoft-server-software-support-for-microsoft-azure-virtual-machines

Azure Prerequisites

The configuration of RRAS is identical to on-premises, with a few additional steps required by Azure infrastructure.

Windows Server

RRAS can be configured on any Windows Server virtual machine supported in Microsoft Azure. As with on-premises deployments, Server GUI and Core are supported. Domain-join is optional. The server can be deployed with one network interface or two.

Public IP

A public IP address must be assigned to the VPN server’s external network interface, or the internal interface if the VPN server is configured with a single network adapter. The IP address can be static or dynamic. When using a dynamic IP address, configure a CNAME record in DNS that points to the name configured for the IP address in Azure. If using a static IP address, an A host record can be configured pointing directly to the IP address.

Network Security Group

A Network Security Group (NSG) must be configured and assigned to the VPN server’s external or public-facing network interface that allows the following protocols and ports inbound.

  • TCP port 443 (SSTP)
  • UDP port 500 (IKEv2)
  • UDP port 4500 (IKEv2 NAT traversal)

RRAS in Azure

Below are the infrastructure requirements for supporting Windows Server RRAS VPN in Azure.

Client IP Subnet

Static IP address pool assignment must be used with RRAS. Using DHCP for VPN client IP address assignment in Azure is not supported and will not work. The IP subnet assigned to VPN clients by RRAS must be unique and not overlap with any existing Azure VNet subnets. If more than one VPN server is deployed, each server should be configured to assign a unique subnet for its clients.

IP Forwarding

IP forwarding must be enabled on the VPN server’s internal network interface. Follow the steps below to enable IP forwarding.

1. In the Azure portal, open the properties page for the internal network interface for the VPN server.
2. Click IP configurations in the navigation pane.
3. Click Enabled next to IP forwarding.
4. Click Save.

Always On VPN and RRAS in Azure

Routing

Azure must be configured to route IP traffic from VPN clients back to the VPN server. Follow the steps below to create and assign a routing table in Azure.

1. Click Create Resource.
2. Enter “Route Table” in the search field and press Enter.
3. Click Route Table.
4. Click Create.
5. Enter a descriptive name for the route table in the Name field.
6. Choose an appropriate subscription from the Subscription drop-down list.
7. Select the resource group where the VPN server(s) reside.
8. Select the best location to deploy the route table resource from the Location drop-down list.
9. If the administrator wants to have the VPN client IP subnet route information published automatically, select Enabled for Virtual network gateway route propagation.
10. Click Create.

Always On VPN and RRAS in Azure

Once complete, follow the steps below to define the route for VPN clients.

1. Open the properties page for the route table.
2. Click Routes in the navigation pane.
3. Click Add.
4. Enter a descriptive name in the Route name filed.
5. Enter the IP subnet assigned to VPN clients in the Address prefix field.
6. Select Virtual appliance from the Next hop type drop-down list.
7. Enter the IPv4 address assigned to the VPN server’s internal network interface in the Next hop address field.
8. Click Ok.
9. Repeat the steps above for each VPN server configured in Azure.

Always On VPN and RRAS in Azure

Finally, follow the steps below to assign the route table to an Azure VNet subnet.

1. Open the properties page for the route table.
2. Click Subnets in the navigation pane.
3. Click Associate.
4. Click Virtual network.
5. Choose the appropriate Azure VNet.
6. Click Subnet.
7. Choose an Azure VNet subnet to assign the route table to.
8. Click Ok.
9. Repeat the steps above to assign the route table to any Azure VNet subnet that must be accessible by VPN clients. If VPN clients need access to on-premises resources via Azure site-to-site gateway, assign the route table to the Azure VPN gateway subnet.

Always On VPN and RRAS in Azure

Note: Azure only supports the assignment of one route table per subnet. If a route table is currently assigned, the VPN client subnet route can be added to an existing route table, if necessary.

Summary

Administrators have many choices when it comes to support Always On VPN connections hosted in Azure. RRAS on Windows Server can be an effective solution, assuming you can live without formal support. If having a formally supported solution is a hard requirement, consider deploying Always On VPN using the native Azure VPN gateway or another third-part Network Virtual Appliance (NVA).

Additional Information

Windows 10 Always On VPN with Azure Gateway

Windows 10 Always On VPN Options for Azure Deployments

Windows 10 Always On VPN Multisite with Azure Traffic Manager

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.

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

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