Azure Virtual Network Hybrid Connections

Azure Hybrid Connections is a feature that allows you to connect your on-premises applications to Azure services, such as Azure App Service and Azure Logic Apps, securely and reliably over the public internet, without requiring complex network configurations like VPNs or ExpressRoute for the initial connection.

Key Concepts

What are Hybrid Connections?

Hybrid Connections provide a secure channel between your on-premises network and Azure. They enable cloud services to reach applications running in your private datacenter. This is achieved by installing a Hybrid Connection Manager (HCM) on your on-premises network, which establishes a persistent outbound connection to Azure Relay. Cloud applications then connect to this relay endpoint, and the traffic is securely tunneled to your on-premises application.

How it Works

1. On-Premises: An agent (Hybrid Connection Manager) is installed on a machine in your on-premises network. This agent makes an outbound HTTPS connection to Azure Relay.
2. Azure Relay: Azure Relay acts as a secure intermediary. It holds the connection open from the on-premises agent and listens for incoming connections from Azure services.
3. Azure Service: When an Azure service (e.g., App Service) needs to connect to your on-premises application, it connects to the Hybrid Connection endpoint in Azure.
4. Secure Tunneling: Azure Relay forwards the traffic from the Azure service through the established outbound connection to your on-premises agent, which then routes it to your application.

This architecture avoids the need for inbound firewall rules on your on-premises network or complex VPN setups for this specific connectivity requirement.

Use Cases

• Connecting Azure App Service web applications to on-premises databases (e.g., SQL Server).
• Enabling Azure Logic Apps to interact with on-premises APIs or services.
• Allowing other Azure services to securely access resources within your private datacenter.

Benefits

• Simplified Connectivity: No need for VPNs or ExpressRoute for hybrid application access.
• Secure by Design: Uses outbound HTTPS connections and Azure Relay for secure tunneling.
• Firewall Friendly: Only requires outbound HTTPS access from the on-premises network.
• Reliable: Azure Relay provides high availability and reliability for the connection.
• Cost-Effective: Often more economical than dedicated network links for specific application connectivity.

Implementing Hybrid Connections

The implementation typically involves the following steps:

1. Create a Hybrid Connection: In the Azure portal, navigate to Azure Relay and create a new Hybrid Connection.
2. Install Hybrid Connection Manager (HCM): Download and install the HCM on an on-premises server.
3. Configure HCM: Configure the HCM with the connection details from your Azure Hybrid Connection.
4. Integrate with Azure Service: Configure your Azure service (e.g., App Service) to use the Hybrid Connection.

Example: Connecting App Service to an On-Premises SQL Server

1. Create an Azure Relay Hybrid Connection.

2. Install and configure the Hybrid Connection Manager (HCM) on a machine within your on-premises network that can reach your SQL Server.

3. In your Azure App Service's connection strings or app settings, use a connection string that targets the Hybrid Connection's hostname and port, but uses the on-premises SQL Server's port (e.g., 1433).

Server=your-hybrid-connection-name.servicebus.windows.net,1433;Database=your_db;User ID=your_user;Password=your_password;

When your App Service attempts to connect to this endpoint, Azure Relay will route the traffic through the HCM to your on-premises SQL Server.

Considerations

• Hybrid Connections are not a replacement for full network connectivity like VPN or ExpressRoute if you need to access a broad range of on-premises resources or require specific network topologies.
• The performance can be influenced by the latency and bandwidth of the public internet connection.
• For high-throughput, low-latency scenarios, or when connecting many services, consider Azure Virtual WAN or ExpressRoute.

For detailed setup and configuration, please refer to the official Azure documentation for Azure Relay and Hybrid Connections.