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Eliminating single points of failure is crucial to ensuring the highest levels of availability for any remote access solution. For Windows 10 Always On VPN deployments, the Windows Server 2016 Routing and Remote Access Service (RRAS) and Network Policy Server (NPS) servers can be load balanced to provide redundancy and high availability within a single datacenter. Additional RRAS and NPS servers can be deployed in another datacenter or in Azure to provide geographic redundancy if one datacenter is unavailable, or to provide access to VPN servers based on the location of the client.
Multisite Always On VPN
Unlike DirectAccess, Windows 10 Always On VPN does not natively include support for multisite. However, enabling multisite geographic redundancy can be implemented using Azure Traffic Manager.
Azure Traffic Manager
Traffic Manager is part of Microsoft’s Azure public cloud solution. It provides Global Server Load Balancing (GSLB) functionality by resolving DNS queries for the VPN public hostname to an IP address of the most optimal VPN server.
Advantages and Disadvantages
Using Azure Traffic manager has some benefits, but it is not with some drawbacks.
Advantages – Azure Traffic Manager is easy to configure and use. It requires no proprietary hardware to procure, manage, and support.
Disadvantages – Azure Traffic Manager offers only limited health check options. Azure Traffic Manager’s HTTPS health check only accepts HTTP 200 OK responses as valid. Most TLS-based VPNs will respond with an HTTP 401 Unauthorized, which Azure Traffic Manager considers “degraded”. The only option for endpoint monitoring is a simple TCP connection to port 443, which is a less accurate indicator of endpoint availability.
Note: This scenario assumes that RRAS with Secure Socket Tunneling Protocol (SSTP) or another third-party TLS-based VPN server is in use. If IKEv2 is to be supported exclusively, it will still be necessary to publish an HTTP or HTTPS-based service for Azure Traffic Manager to monitor site availability.
Traffic Routing Methods
Azure Traffic Manager provide four different methods for routing traffic.
Priority – Select this option to provide active/passive failover. A primary VPN server is defined to which all traffic is routed. If the primary server is unavailable, traffic will be routed to another backup server.
Weighted – Select this option to provide active/active failover. Traffic is routed to all VPN servers equally, or unequally if desired. The administrator defines the percentage of traffic routed to each server.
Performance – Select this option to route traffic to the VPN server with the lowest latency. This ensures VPN clients connect to the server that responds the quickest.
Geographic – Select this option to route traffic to a VPN server based on the VPN client’s physical location.
Configure Azure Traffic Manager
Open the Azure management portal and follow the steps below to configure Azure Traffic Manager for multisite Windows 10 Always On VPN.
Create a Traffic Manager Resource
- Click Create a resource.
- Click Networking.
- Click Traffic Manager profile.
Create a Traffic Manager Profile
- Enter a unique name for the Traffic Manager profile.
- Select an appropriate routing method (described above).
- Select a subscription.
- Create or select a resource group.
- Select a resource group location.
- Click Create.
Important Note: The name of the Traffic Manager profile cannot be used by VPN clients to connect to the VPN server, since a TLS certificate cannot be obtained for the trafficmanager.net domain. Instead, create a CNAME DNS record that points to the Traffic Manager FQDN and ensure that name matches the subject or a Subject Alternative Name (SAN) entry on the VPN server’s TLS and/or IKEv2 certificates.
Endpoint Monitoring
Open the newly created Traffic Manager profile and perform the following tasks to enable endpoint monitoring.
- Click Configuration.
- Select TCP from the Protocol drop-down list.
- Enter 443 in the Port field.
- Update any additional settings, such as DNS TTL, probing interval, tolerated number of failures, and probe timeout, as required.
- Click Save.
Endpoint Configuration
Follow the steps below to add VPN endpoints to the Traffic Manager profile.
- Click Endpoints.
- Click Add.
- Select External Endpoint from the Type drop-down list.
- Enter a descriptive name for the endpoint.
- Enter the Fully Qualified Domain Name (FQDN) or the IP address of the first VPN server.
- Select a geography from the Location drop-down list.
- Click OK.
- Repeat the steps above for any additional datacenters where VPN servers are deployed.
Summary
Implementing multisite by placing VPN servers is multiple physical locations will ensure that VPN connections can be established successfully even when an entire datacenter is offline. In addition, active/active scenarios can be implemented, where VPN client connections can be routed to the most optimal datacenter based on a variety of parameters, including current server load or the client’s current location.
Windows 10 clients include full support for all enterprise DirectAccess scalability and redundancy features, including automatic site selection and transparent failover for multisite deployments. However, the native site selection process is limited in functionality and often yields unexpected results.
NetScaler is an excellent platform that can be configured to improve upon native DirectAccess high availability and redundancy features. It provides superior load balancing compared to native Windows Network Load Balancing (NLB), with more throughput and better traffic visibility, while at the same time reducing resource utilization on the DirectAccess server.
To provide geographic redundancy, DirectAccess can be deployed in a multisite configuration. In this scenario, Windows 8.x and Windows 10 clients are aware of all entry points in the enterprise and will automatically select the nearest available entry point to connect to. The nearest entry point is defined as the one that responds the quickest. When a Windows 8.x or Windows 10 client attempts to establish DirectAccess connectivity, an HTTP GET is sent to all entry points and the client will select the one with the shortest Round Trip Time (RTT) for the request.
DirectAccess has been with us for quite some time know, having been originally introduced with Windows Server 2008 R2, later enhanced with Forefront Unified Access Gateway (UAG) 2010, and finally integrated in to the base operating system in Windows Server 2012 R2. Client support for DirectAccess begins with Windows 7 (Enterprise or Ultimate), and also includes Windows 8.x (Enterprise) and Windows 10 (Enterprise or Education).
