Public and private networking zones in Azure: Understanding the differences

In the realm of public cloud providers such as Azure, networking zones play a critical role in how resources are accessed and secured. As a cloud engineer, it's essential to understand the distinction between private and public networking zones and how to configure cloud resources for either to meet business requirements. 

In this article, we’ll cover the differences between these two networking zones and show how different Azure services interact with them. We’ll use Azure as our public cloud example, but these concepts apply to various public clouds.

• Understanding the public networking zone in Azure
• Understanding the private networking zone in Azure
• Integrating private and public cloud services
• Conclusion: Build your Azure cloud skills

The public networking zone in Azure is where resources are exposed to the internet through public endpoints, such as storageaccount.blob.core.windows.net for the blob sub-service in our Azure storage accounts. 

Behind the scenes, this public endpoint is associated with a set of dynamically allocated public IPs. These dynamic public IPs are managed by Microsoft. We simply use the FQDN endpoint to reference these resources and eliminate the tedious task of keeping up with dynamic public IPs. 

As you can see from this example, this public networking zone is typically used for services that need to be accessible by users or applications over the internet.

Below are some key services that use the public zone for connectivity.

• Azure Storage accounts: By default, Azure Storage accounts are accessible via public endpoints. This means that anyone with the proper credentials can access the storage account over the internet.

• Azure Web Apps: These apps are designed to be internet facing, providing web applications and APIs to users globally.

• Azure SQL Database: While Azure SQL Database can be configured for private access, it’s often accessible through a public endpoint for ease of connectivity.

Example: An e-commerce website hosted on Azure Web Apps uses the public networking zone to serve content to users worldwide. Its Azure Storage account, which stores product images, is also accessible via a public endpoint.

Now that we have an understanding of the public networking zone in Azure, it’s time for the private networking zone. This private networking zone is designed for internal communications within your Azure environment or between your on-premises network and Azure. 

Resources in this zone are assigned private IP addresses and are not accessible from the internet by default, enhancing security and control as a result. This private networking zone can also be referred to as a Virtual Network (VNet). 

In Azure, Virtual Networks are the isolated private networks that we use for private resources such as Azure VMs, other resources we want to privately connect to with our VNets, and resources in on-premises networks in hybrid networking environments.

Here are some key services in the private networking zone and an example use case for context.

• Azure Virtual Machines (VMs): By default, Azure VMs are deployed within a Virtual Network and assigned private IP addresses. This allows secure communication between VMs and other resources within the VNet.

• Azure SQL Database with Private Link: When configured with private endpoints, Azure SQL Database can be accessed securely from within a VNet, avoiding exposure to the public internet.

• Azure Kubernetes Service (AKS): Deployed within a VNet, AKS clusters can be configured to use private IP addresses for secure internal communication.

Example: A company's internal Customer Relationship Management (CRM) application runs on Azure VMs within a VNet. It’s accessible only by employees via a secure VPN connection, ensuring that sensitive customer data remains protected.

At this point, you should understand the differences between the public and private networking zones. But how do you integrate between these zones? 

In Azure, we have the option for flexible configurations. Resources can be projected into both public and/or private zones, depending on the needs of your application. Here are some examples of integrating public services into the private network zone and integrating private resources into the public network zone.

Many Azure PaaS services, such as Azure Storage and Azure SQL Database, can be integrated into the private networking zone using private endpoints. This allows apps or users to access these services using private IP addresses within a VNet, enhancing security by avoiding public internet exposure.

Example: An Azure Storage account is configured with a private endpoint, making it accessible only within the company's VNet. This setup ensures that only applications and users within the VNet can access the storage account.

Conversely, resources typically in the private zone, like Azure VMs, can be made accessible from the internet by assigning them public IP addresses. This is useful for scenarios where specific VMs need to be accessed remotely.

Example: A development team requires remote access to an Azure VM for testing purposes. By assigning a public IP address to the VM, the team can securely access the VM over the internet while still leveraging network security groups and Azure Firewall for protection.

In conclusion, understanding the differences between private and public networking zones in Azure is crucial for designing secure, scalable, and high-performance cloud architectures. By leveraging these zones appropriately, you ensure that your applications and services are accessible while maintaining robust network security.

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