Azure Private Link Endpoints: Where to Use

Azure Private Link provides private connectivity from your virtual network to Azure platform as a service (PaaS) and Azure managed services, as well as to customer-owned or partner services, all over the Microsoft backbone network. This offers enhanced security and a simplified network architecture by eliminating exposure to the public internet.

Private Link endpoints are virtual network interfaces that you create in your virtual network. Each endpoint represents an instance of a specific Azure service. This document outlines common scenarios and use cases for Azure Private Link endpoints.

Key Scenarios and Use Cases

1. Securing Access to Azure PaaS Services

This is the most common and powerful use case for Private Link. Instead of accessing services like Azure Storage, Azure SQL Database, or Azure Cosmos DB over their public endpoints, you can route traffic through a private endpoint within your virtual network. This ensures that data transfer happens entirely within the Azure network, never traversing the public internet.

• Azure Storage: Securely access blobs, files, queues, and tables without exposing storage accounts publicly.
• Azure SQL Database & Managed Instance: Connect to your databases privately, crucial for sensitive financial or healthcare data.
• Azure Cosmos DB: Provide private access to your globally distributed NoSQL database.
• Azure Key Vault: Securely retrieve secrets, keys, and certificates without public exposure.
• Azure Event Hubs & Service Bus: Stream events and send messages privately for real-time data processing and application integration.

2. Connecting to Your Own Services Hosted on Azure

If you host your own applications or services within Azure (e.g., on Azure Virtual Machines, Azure Kubernetes Service, or Azure App Service), you can use Private Link to create private endpoints that your other Azure resources can connect to. This allows internal services to communicate securely without needing public IP addresses or complex network security group rules for external access.

• Multi-tier applications: A web application in one subnet accessing a backend database in another subnet via private endpoints.
• Microservices communication: Services within AKS or App Service connecting to other internal services securely.

3. Connecting to Partner and Customer-Owned Services

Azure Private Link also enables you to consume services hosted by third-party vendors or other organizations within Azure. If a partner offers a service (e.g., a SaaS application, a data analytics platform) and exposes it via Private Link, you can create a private endpoint in your virtual network to access it securely.

• SaaS integration: Securely connect to SaaS applications without public internet exposure.
• Data sharing: Access shared data services from trusted partners privately.

4. Simplifying Network Architecture and Reducing Attack Surface

By replacing public endpoints with private endpoints, you significantly reduce your network's attack surface. Network security teams no longer need to manage complex firewall rules for public access, and the risk of man-in-the-middle attacks or unauthorized access from the internet is mitigated.

• On-premises connectivity: Combine Private Link with Azure ExpressRoute or VPN Gateway for seamless private access from your on-premises networks to Azure services.
• Network segmentation: Enforce strict network policies by isolating service access within virtual networks.

When to Consider Using Private Link Endpoints

• When you need to prevent data exfiltration or unauthorized access to Azure services.
• When your compliance requirements mandate that sensitive data never traverses the public internet.
• When you want to simplify your network security posture by reducing public exposure.
• When you are building multi-tier applications and need secure inter-service communication within Azure.
• When integrating with partner or customer-owned services that support Private Link.
• When you want to leverage the Microsoft backbone network for reliable and low-latency private connectivity.

Example: Securing Azure SQL Database Access

Imagine a financial application running in Azure that requires access to an Azure SQL Database. Without Private Link, the SQL database would need a public endpoint accessible over the internet, protected by firewall rules. With Private Link, you would:

1. Create an Azure SQL Database.
2. In your virtual network, create a Private Endpoint for the Azure SQL Database. This assigns a private IP address from your VNet to the SQL Database.
3. Configure your application within the VNet to connect to the SQL Database using its private IP address or FQDN.

This ensures that traffic between your application and the SQL Database stays entirely within the Azure network, providing robust security and compliance.