Always On VPN IPsec Root Certificate Configuration Issue

Always On VPN Device Tunnel Status IndicatorWhen configuring a Windows Routing and Remote Access Service (RRAS) server to support Internet Key Exchange version 2 (IKEv2) VPN connections, it is essential for the administrator to define the root certification authority for which to accept IPsec security associations (SAs). Without defining this setting, the VPN server will accept a device certificate issued by any root certification authority defined in the Trusted Root Certification Authorities store. Details about configuring IKEv2 security and defining the root certification authority can be found here.

Multiple Root Certificates

Administrators may find that when they try to define a specific root certification authority, the setting may not be implemented as expected. This commonly occurs when there is more than one root certificate in the Trusted Root Certification Authorities store for the same PKI.

Always On VPN IPsec Root Certificate Configuration Issue

Certificate Selection

When running the PowerShell command Set-VpnAuthProtocol to define the root certification authority, PowerShell may ignore the administrator-defined certificate and choose a different one, as shown here. This will result in failed IPsec VPN connections from Windows 10 Always On VPN clients using IKEv2.

Always On VPN IPsec Root Certificate Configuration Issue

Certificate Publishing

This issue can occur when root certification authority certificates are published using Active Directory group policy. It appears that Windows prefers Active Directory group policy published certificates over those published directly in the Certification Authorities Container in Active Directory. To resolve this issue, remove any group policy objects that are publishing root certification authority certificates and ensure those root certificates are published in the Certification Authorities container in Active Directory.

PowerShell Script

A PowerShell script to configure this setting that can be found in my Always On VPN GitHub repository here. I have updated this script to validate the defined root certification authority certificate and warn the user if it does not match.

Additional Information

Set-Ikev2VpnRootCertificate.ps1 PowerShell script on GitHub

Windows 10 Always On VPN IKEv2 Security Configuration

Windows 10 Always On VPN IKEv2 Load Balancing and NAT

Windows 10 Always On VPN IKEv2 Features and Limitations

Windows 10 Always On VPN IKEv2 Fragmentation

Windows 10 Always On VPN IKEv2 Certificate Requirements

Always On VPN IKEv2 Load Balancing and NAT

Always On VPN IKEv2 Load Balancing and NATOver the last few weeks, I’ve worked with numerous organizations and individuals troubleshooting connectivity and performance issues associated with Windows 10 Always On VPN, and specifically connections using the Internet Key Exchange version 2 (IKEv2) VPN protocol. An issue that appears with some regularity is when Windows 10 clients fail to connect with error 809. In this scenario, the server will accept connections without issue for a period of time and then suddenly stop accepting requests. When this happens, existing connections continue to work without issue in most cases. Frequently this occurs with Windows Server Routing and Remote Access Service (RRAS) servers configured in a clustered array behind an External Load Balancer (ELB).

Network Address Translation

It is not uncommon to use Network Address Translation (NAT) when configuring Always On VPN. In fact, for most deployments the public IP address for the VPN server resides not on the VPN server, but on an edge firewall or load balancer connected directly to the Internet. The firewall/load balancer is then configured to translate the destination address to the private IP address assigned to the VPN server in the perimeter/DMZ or the internal network. This is known a Destination NAT (DNAT). Using this configuration, the client’s original source IP address is left intact. This configuration presents no issues for Always On VPN.

Source Address Translation

When troubleshooting these issues, the common denominator seems to be the use of Full NAT, which includes translating the source address in addition to the destination. This results in VPN client requests arriving at the VPN server as appearing not to come from the client’s original IP address, but the IP address of the network device (firewall or load balancer) that is translating the request. Full NAT may be explicitly configured by an administrator, or in the case of many load balancers, configured implicitly because the load balancer is effectively proxying the connection.

Known Issues

IKEv2 VPN connections use IPsec for encryption, and by default, Windows limits the number of IPsec Security Associations (SAs) coming from a single IP address. When a NAT device is performing destination/full NAT, the VPN server sees all inbound IKEv2 VPN requests as coming from the same IP address. When this happens, clients connecting using IKEv2 may fail to connect, most commonly when the server is under moderate to heavy load.

Resolution

The way to resolve this issue is to ensure that any load balancers or NAT devices are not translating the source address but are performing destination NAT only. The following is configuration guidance for F5, Citrix ADC (formerly NetScaler), and Kemp load balancers.

F5

On the F5 BIG-IP load balancer, navigate to the Properties > Configuration page of the IKEv2 UDP 500 virtual server and choose None from the Source Address Translation drop-down list. Repeat this step for the IKEv2 UDP 4500 virtual server.

Always On VPN IKEv2 Load Balancing and NAT

Citrix ADC

On the Citrix ADC load balancer, navigate to System > Settings > Configure Modes and check the option to Use Subnet IP.

Always On VPN IKEv2 Load Balancing and NAT

Next, navigate to Traffic Management > Load Balancing > Service Groups and select the IKEv2 UDP 500 service group. In the Settings section click edit and select Use Client IP. Repeat these steps for the IKEv2 UDP 4500 service group.

Always On VPN IKEv2 Load Balancing and NAT

Kemp

On the Kemp LoadMaster load balancer, navigate to Virtual Services > View/Modify Services and click Modify on the IKEv2 UDP 500 virtual service. Expand Standard Options and select Transparency. Repeat this step for the IKEv2 UDP 4500 virtual service.

Always On VPN IKEv2 Load Balancing and NAT

Caveat

Making the changes above may introduce routing issues in your environment. When configuring these settings, it may be necessary to configure the VPN server’s default gateway to use the load balancer to ensure proper routing. If this is not possible, consider implementing the workaround below.

Workaround

To fully resolve this issue the above changes should be made to ensure the VPN server can see the client’s original source IP address. If that’s not possible for any reason, the following registry key can be configured to increase the number of established SAs from a single IP address. Be advised this is only a partial workaround and may not fully eliminate failed IKEv2 connections. There are other settings in Windows that can prevent multiple connections from a single IP address which are not adjustable at this time.

To implement this registry change, open an elevated PowerShell command window on the RRAS server and run the following commands. Repeat these commands on all RRAS servers in the organization.

New-ItemProperty -Path ‘HKLM:SYSTEM\CurrentControlSet\Services\IKEEXT\Parameters\’ -Name IkeNumEstablishedForInitialQuery -PropertyType DWORD -Value 50000 -Force

Restart-Service IKEEXT -Force -PassThru

Additional Information

IPsec Traffic May Be Blocked When A Computer is Behind a Load Balancer

Windows 10 Always On VPN IKEv2 Load Balancing with Citrix NetScaler ADC

Windows 10 Always On VPN IKEv2 Load Balancing with F5 BIG-IP

Windows 10 Always On VPN IKEv2 Load Balancing with Kemp LoadMaster

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 ADC (formerly 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 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

Always On VPN RRAS Monitoring and Reporting

Always On VPN RRAS Monitoring and ReportingWindows Server with the Routing and Remote Access Service (RRAS) role installed is a popular choice for Windows 10 Always On VPN deployments. Configuring RRAS is commonly performed using the RRAS management console but it can also be configured using PowerShell and/or netsh. In addition, there are a few different options for natively monitoring server health and client connection status.

RRAS Management Console

After installing the RRAS role, the administrator uses the RRAS management console (rrasmgmt.msc) to perform initial configuration. The RRAS management console can also be used to view client connection status by expanding the server and highlighting Remote Access Clients.

Connection Details

To view connection details for a specific connection, the administrator can right-click a connection and choose Status, or simply double-click the connection.

High level information about the connection including duration, data transfer, errors, and IP address assignment can be obtained here. In addition, the administrator can terminate the VPN connection by clicking the Disconnect button.

RRAS Management Console Limitations

Using the RRAS management console has some serious limitations. It offers only limited visibility into client connectivity status, for example. In addition, the client connection status does not refresh automatically. Also, the RRAS management console offers no historical reporting capability.

Remote Access Management Console

The Remote Access Management console (ramgmtui.exe) will be familiar to DirectAccess administrators and is a better option for viewing VPN client connectivity on the RRAS server. It also offers more detailed information on connectivity status and includes an option to enable historical reporting.

Dashboard

The Dashboard node in the Remote Access Management console provides high-level status for various services associated with the VPN server. It also provides a high-level overview of aggregate VPN client connections.

Operations Status

The Operations Status node in the Remote Access Management console provides more detailed information regarding the status of crucial VPN services. Here the administrator will find current status and information about service uptime.

Remote Client Status

The Remote Client Status node in the Remote Access Management console is where administrators will find detailed information about client connectivity. Selecting a connection will provide data about the connection including remote IP addresses, protocols, and ports accessed by the remote client, in addition to detailed connection information such as authentication type, public IP address (if available), connection start time, and data transferred.

Always On VPN RRAS Monitoring and Reporting

Double-clicking an individual connection brings up a detailed client statistics page for the connection, as shown here.

Always On VPN RRAS Monitoring and Reporting

Custom View

The Remote Access Management console includes the option to customize the data presented to the administrator. To view additional details about client connections, right-click anywhere in the column headings to enable or disable any of the fields as required.

Always On VPN RRAS Monitoring and Reporting

Recommended Columns

From personal experience I recommend adding the following columns in the Remote Access Management console.

  • IPv4 Address (this is the IP address assigned to the VPN clients by RRAS)
  • Connection Start Time
  • Authentication Method
  • Total Bytes In
  • Total Bytes Out
  • Rate

Always On VPN RRAS Monitoring and Reporting

Drawbacks

The only real drawback to using the Remote Access Management console is that it supports viewing connections from just one VPN server at a time. If you have multiple RRAS servers deployed, you must retarget the Remote Access Management console each time to view connections on different VPN servers in the organization.

You can retarget the Remote Access Management console at any time by highlighting the Configuration node in the navigation pane and then clicking the Manage a Remote Server link in the Tasks pane.

Always On VPN RRAS Monitoring and Reporting

Reporting

Remote Access reporting is not enabled by default on the RRAS VPN server. Follow the steps below to enable historical reporting for RRAS VPN connections.

1. Highlight the Reporting node in the Remote Access Management console.
2. Click Configure Accounting.
3. Uncheck Use RADIUS accounting.
4. Check Use inbox accounting.
5. Review the settings for data retention and make changes as required.
6. Click Apply.

Always On VPN RRAS Monitoring and Reporting

Optionally, historical reporting can be enabled using PowerShell by opening and elevated PowerShell command window and running the following command.

Set-RemoteAccessAccounting -EnableAccountingType Inbox -PassThru

Important Note! There is a known issue with the inbox accounting database that can result in high CPU utilization for very busy RRAS VPN servers. Specifically, a crucial index is missing from one of the tables in the logging database. To correct this issue, download and run the Optimize-InboxAccountingDatabase.ps1 script on each RRAS VPN server in the organization.

Additional Information

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

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

Windows 10 Always On VPN and RRAS with Single NIC

Windows 10 Always On VPN and RRAS in Microsoft Azure

Always On VPN IKEv2 Load Balancing Issue with Kemp LoadMaster

Always On VPN IKEv2 Load Balancing Issue with Kemp LoadMasterA recent update to the Kemp LoadMaster load balancer may cause failed connections for Always On VPN connections using IKEv2. SSTP VPN connections are unaffected.

Load Balancing IKEv2

When using the Kemp LoadMaster load balancer to load balance IKEv2, custom configuration is required to ensure proper operation. Specifically, the virtual service must be configured to use “port following” to ensure both the initial request on UDP port 500 and the subsequent request on UDP port 4500 are sent to the same real server. This requires the virtual service to be configured to operate at layer 7. Detailed configuration guidance for load balancing IKEv2 on the Kemp LoadMaster load balancer can be found here.

Always On VPN IKEv2 Load Balancing Issue with Kemp LoadMaster

Issues with LMOS 7.2.48.0

A recent release of the Load Master Operating System (LMOS) v7.2.48.0 introduced a bug that affects UDP services configured to operate at layer 7, which includes IKEv2. This bug breaks Always On VPN connections using IKEv2, resulting in failed connections. When this occurs, the administrator may encounter an error 809 message for device tunnel or user tunnel.

Always On VPN IKEv2 Load Balancing Issue with Kemp LoadMaster

Update Available

Administrators who use the Kemp LoadMaster load balancer to load balance Always On VPN IKEv2 connections and have updated to LMOS 7.2.48.0 are encouraged to update to LMOS 7.2.48.1 immediately. This latest update includes a fix that resolves broken IKEv2 load balancing for Always On VPN. Once the LoadMaster has been updated to 7.2.48.1, Always On VPN connections using IKEv2 should complete successfully.

Additional Information

Windows 10 Always On VPN IKEv2 Load Balancing and NAT

Windows 10 Always On VPN IKEv2 Load Balancing with Kemp LoadMaster Load Balancer

Windows 10 Always On VPN SSTP Load Balancing with Kemp LoadMaster Load Balancer

Windows 10 Always On VPN Load Balancing with Kemp LoadMaster in Azure

Windows 10 Always On VPN Load Balancing Deployment Guide for Kemp Load Balancers

Always On VPN Load Balancing with Kemp in Azure

Always On VPN Load Balancing with Kemp in AzureIn a recent post I discussed options for load balancing Windows Server Routing and Remote Access Service (RRAS) in Microsoft Azure for Always On VPN. There are many choices available to the administrator, however the best alternative is to use a dedicated Application Delivery Controller (ADC), or load balancer. The Kemp LoadMaster load balancer is an excellent choice here, as it is easy to configure and deploy. It is also very cost effective and offers flexible licensing plans, including a metered licensing option.

Deploy LoadMaster in Azure

To provision a Kemp LoadMaster load balancer in Microsoft Azure, open the Azure management console and perform the following steps.

1. Click Create Resource.
2. Enter LoadMaster in the search field.
3. Click on LoadMaster Load Balancer ADC Content Switch.

Always On VPN Load Balancing with Kemp in Azure

4. Choose an appropriate license model from the Select a software plan drop-down list.
5. Click Create.

Prepare Azure Instance

Follow the steps below to provision the Azure VM hosting the Kemp LoadMaster load balancer.

1. Choose an Azure subscription to and resource group to deploy the resources to.
2. Provide instance details such as virtual machine name, region, availability options, and image size.
3. Select an authentication type and upload the SSH private key or provide a username and password.
4. Click Next:Disks >.

Always On VPN Load Balancing with Kemp in Azure

5. Select an OS disk type.
6. Click Next: Networking >.

Always On VPN Load Balancing with Kemp in Azure

7. Select a virtual network and subnet for the load balancer.
8. Create or assign a public IP address.
9. Click Review + create.

Always On VPN Load Balancing with Kemp in Azure

LoadMaster Configuration

Once the virtual machine has been provisioned, open a web browser and navigate to the VM’s internal IP address on port 8443 to accept the licensing terms.

Always On VPN Load Balancing with Kemp in Azure

Next, log in with your Kemp ID and password to finish licensing the appliance.

Always On VPN Load Balancing with Kemp in Azure

Finally, log in to the appliance using the username ‘bal’ and the password provided when the virtual machine was configured.

Always On VPN Load Balancing with Kemp in Azure

Azure Network Security Group

A Network Security Group (NSG) is automatically configured and associated with the LoadMaster’s network interface when the appliance is created. Additional inbound security rules must be added to allow VPN client connectivity.

In the Azure management console open the properties for the LoadMaster NSG and follow the steps below to configure security rules to allow inbound VPN protocols.

SSTP

1. Click Inbound security rules.
2. Click Add.
3. Choose Any from the Source drop-down list.
4. Enter * in the Source port ranges field.
5. Select Any from the Destination drop-down list.
6. Enter 443 in the Destination port ranges field.
7. Select the TCP protocol.
8. Select the Allow action.
9. Enter a value in the Priority field.
10. Enter a name for the service in the Name field.
11. Click Add.

Always On VPN Load Balancing with Kemp in Azure

IKEv2

1. Click Inbound security rules.
2. Click Add.
3. Choose Any from the Source drop-down list.
4. Enter * in the Source port ranges field.
5. Select Any from the Destination drop-down list.
6. Enter 500 in the Destination port ranges field.
7. Select the UDP protocol.
8. Select the Allow action.
9. Enter a value in the Priority field.
10. Enter a name for the service in the Name field.
11. Click Add.
12. Repeat the steps below for UDP port 4500.

Always On VPN Load Balancing with Kemp in Azure

Load Balancing SSTP and IKEv2

Refer to the following posts for detailed, prescriptive guidance for configuring the Kemp LoadMaster load balancer for Always On VPN load balancing.

Always On VPN SSTP Load Balancing with Kemp LoadMaster

Always On VPN IKEv2 Load Balancing with the Kemp LoadMaster

Always On VPN Load Balancing Deployment Guide for the Kemp LoadMaster

Summary

Although Windows Server RRAS is not a formally supported workload in Azure, it is still a popular and effective solution for Always On VPN deployments. The Kemp LoadMaster load balancer can be deployed quickly and easily to provide redundancy and increase scalability for larger deployments.

Additional Information

Windows 10 Always On VPN SSTP Load Balancing with Kemp LoadMaster Load Balancers

Windows 10 Always On VPN IKEv2 Load Balancing with Kemp LoadMaster Load Balancers

Windows 10 Always On VPN Load Balancing Deployment Guide for Kemp LoadMaster Load Balancers

Deploying the Kemp LoadMaster Load Balancer in Microsoft Azure

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 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

You can also find PowerShell script to import and export RRAS configuration on my Github.

Export-VpnServerConfiguration.ps1

Import-VpnServerConfiguration.ps1

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)

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