Deploying an SSTP VPN on Azure Virtual Machines requires careful planning across networking, certificates, OS configuration, and Azure platform components. This guide walks site owners, enterprise IT teams, and developers through a practical, step-by-step process for building a secure and maintainable SSTP server on an Azure VM. It includes hands-on configuration, automation tips, and troubleshooting practices to ensure reliable connectivity and security.

Why SSTP on Azure?

SSTP (Secure Socket Tunneling Protocol) encapsulates PPP traffic over HTTPS (TCP/443), allowing VPN connections to traverse restrictive firewalls and proxies that block other VPN types. For organizations that need a dependable client-to-site solution from Windows clients (native SSTP support) and interoperability with mobile/third-party clients, SSTP on Azure VMs provides a flexible option without managed VPN service limitations.

Prerequisites and Planning

Before provisioning resources, verify the following:

  • Azure subscription with permissions to create VMs, Public IPs, Network Security Groups (NSGs), and Virtual Networks (VNets).
  • A Windows Server image (2016/2019/2022) or Windows Server Core if you prefer minimal GUI. RRAS (Routing and Remote Access Service) runs on Windows Server.
  • A purchased domain name and DNS control to map a public FQDN to the VM’s public IP. A stable FQDN is recommended for certificate provisioning.
  • An SSL/TLS certificate for the SSTP listener that matches the VM FQDN (recommended: certificate issued by a public CA). Self-signed certs are possible for testing but require client trust configuration.
  • Network design: consider subnet segmentation, backend resource connectivity, and gateway architecture (single VM vs. high-availability pair behind load balancer).

Step 1 — Create the Azure Virtual Machine and Networking

1. Create a new Virtual Network and Subnet for the VPN VM. Use address ranges that do not conflict with client networks to avoid overlapping routes.

2. Deploy a Windows Server VM with a static private IP within the subnet. For predictable DNS/certificate mapping, assign a static public IP resource (or use Azure DNS and update records when needed).

3. Configure an Azure Network Security Group (NSG):

  • Allow inbound TCP 443 (SSTP) from 0.0.0.0/0 or a defined set of client IP ranges.
  • Allow inbound RDP (3389) from trusted administrative IPs only.
  • Block unnecessary inbound traffic (minimize attack surface).

Public IP and DNS

Reserve a static Public IP and create a DNS A record pointing your chosen FQDN (e.g., vpn.example.com) to that IP. This FQDN must match the SSTP certificate’s common name (CN) or SAN.

Step 2 — Obtain and Install an SSL/TLS Certificate

SSTP requires a server certificate for SSL. Use one of the following approaches:

  • Public CA certificate: Buy a certificate for vpn.example.com and install it into the Local Computer\Personal store.
  • Let’s Encrypt: Use a Windows ACME client to obtain a certificate. Note: Let’s Encrypt requires automated renewal and an HTTP or DNS validation method.
  • Internal CA: Use corporate PKI and distribute the CA root to clients.

Install the certificate on the VM and ensure the private key is exportable or accessible to RRAS. Record the certificate’s thumbprint; you’ll use it to bind SSTP if needed.

Step 3 — Configure RRAS for SSTP

1. Install the Remote Access role via Server Manager or PowerShell:

  • Server Manager > Add Roles and Features > Remote Access > VPN (and DirectAccess if needed).
  • Or PowerShell: Install-WindowsFeature -Name RemoteAccess -IncludeManagementTools then Install-WindowsFeature -Name Routing -IncludeManagementTools.

2. Open the Routing and Remote Access management console (rrasmgmt.msc) and configure as follows:

  • Right-click server > Configure and Enable Routing and Remote Access.
  • Select “Custom configuration” > check “VPN access” and optionally “NAT”.
  • Start the service when prompted.

3. Configure SSTP listener binding:

  • Under Ports > Properties > WAN Miniport (SSTP) ensure at least one port is enabled.
  • Bind the installed certificate to SSTP if RRAS doesn’t auto-detect it: use the certificate thumbprint and netsh http add sslcert commands to bind to the listening IP/443.

Using netsh to bind the certificate

Example command (run in an elevated PowerShell):

netsh http add sslcert ipport=0.0.0.0:443 certhash=<thumbprint> appid={YOUR-GUID-HERE}

Replace <thumbprint> with your cert thumbprint (remove spaces) and supply a GUID for appid. This ensures Windows listens with the given cert on port 443.

Step 4 — Configure Address Assignment and Routing

Define how VPN clients receive IP addresses and how traffic is routed:

  • Use DHCP relay or static address pool in RRAS (properties > IPv4 > Static address pool). Ensure the pool does not overlap with the Azure subnet or on-prem network.
  • Optionally configure NAT on the RRAS server to allow clients to access the internet via the VM. Use NAT only if required and consider Azure cost/throughput.
  • Set up routes on your backend networks or Azure route tables if you require client-to-VNet connectivity. You may need to add UDRs (User Defined Routes) for return traffic to the VPN subnet.

Step 5 — Azure Platform Considerations

1. NSGs and Azure Firewall: Confirm NSG rules allow inbound TCP 443 and outbound traffic as needed. If Azure Firewall or third-party appliances are in front of the VM, create corresponding rules and DNAT for port 443 to the VM private IP.

2. Load Balancer for HA: For high availability, place two or more RRAS VMs behind an Azure Standard Load Balancer with a floating IP (direct server return) configuration. Use custom probe and inbound NAT rules—SSTP over load balancer requires careful configuration to maintain SSL state.

3. Diagnostics and metrics: Enable Boot Diagnostics and collect network metrics, NSG flow logs, and VM diagnostics for monitoring and troubleshooting.

Step 6 — Client Configuration

On Windows clients:

  • Control Panel > Network and Sharing Center > Set up a new connection or network > Connect to a workplace > Use my Internet connection (VPN).
  • Enter the server address (vpn.example.com) and set VPN type to SSTP (Secure Socket Tunneling Protocol) or use Automatic with SSTP prioritized.
  • Import the server certificate root if using internal/ self-signed certs.

Mobile and third-party clients may require SSTP-compatible implementations (e.g., open-source or vendor clients). Test connectivity, authentication, and resource access thoroughly.

Troubleshooting Common Issues

Certificate Errors

Symptom: Clients cannot establish SSL connection or show certificate mismatch.

  • Verify FQDN matches certificate CN/SAN.
  • Confirm the certificate is installed in Local Computer\Personal and private key is present.
  • Check certificate chain and ensure clients trust the issuing CA.

Port/Connectivity Issues

Symptom: TCP 443 seems blocked or connection times out.

  • Confirm NSG inbound rule for TCP 443 exists and has higher priority than deny rules.
  • Check Azure Firewall/NVA or corporate perimeter firewall for blocking rules.
  • Use telnet/netcat from an external location to test connectivity on port 443 to the Public IP.

IP Assignment and Routing Problems

Symptom: Client connects but has no internet or cannot reach VNet resources.

  • Verify RRAS IP pool does not overlap with VNet addressing.
  • If using NAT, ensure NAT is configured and Azure UDRs direct return traffic appropriately.
  • Check client routing table (route print on Windows) to confirm routes are assigned.

Automation and Infrastructure as Code

To streamline deployments and maintain consistency, use IaC tools:

  • ARM Templates or Bicep: automate VM, Public IP, NSG, and load balancer provisioning.
  • PowerShell DSC or Ansible: automate Windows role installation, RRAS configuration, and certificate installation.
  • Use Azure Key Vault to store certificates and secrets securely; automate certificate retrieval and installation onto VM during provisioning.

Example workflow: deploy resources via Bicep, provision VM extensions to run a PowerShell script that fetches certificate from Key Vault, installs it, and configures RRAS and netsh bindings.

Security Best Practices

  • Use public CA certificates where possible to avoid client trust issues; automate renewals (ACME/Let’s Encrypt clients or Azure Key Vault Certificates).
  • Limit administrative access to the VM using Just-In-Time (JIT) VM access or strict NSG rules.
  • Enable Azure Backup and OS-level hardening (Windows updates, minimize installed roles).
  • Monitor logs: enable RRAS logging, NSG flow logs, and Azure Monitor alerts for suspicious behavior.
  • Enforce strong authentication—consider integrating with Azure AD, RADIUS, or certificate-based client authentication for higher assurance.

Performance and Scale Considerations

Throughput is tied to VM size and Azure networking constraints. For sites with many concurrent users or heavy throughput, use larger VM SKUs with accelerated networking and consider a multi-VM, load-balanced design. Monitor CPU, memory, and network interfaces and scale vertically or horizontally as needed.

Final Checklist Before Go-Live

  • Public FQDN mapped to static Public IP
  • Valid certificate installed and bound to TCP/443
  • NSG and Azure Firewall rules permitting SSTP traffic
  • RRAS configured with address assignment and authentication (local, AD, or RADIUS)
  • Monitoring and backups enabled
  • Documented recovery and certificate renewal procedures

Deploying SSTP on Azure VMs provides a robust and firewall-friendly VPN solution suitable for many enterprise needs. Careful attention to certificates, Azure networking, and RRAS configuration will yield a secure, maintainable service. For orchestration, use ARM/Bicep templates and configuration management to ensure repeatable, auditable deployments.

For more guides and tools related to dedicated IP VPNs and secure connectivity, visit Dedicated-IP-VPN at https://dedicated-ip-vpn.com/.