Last Updated on August 13, 2025 by Arnav Sharma
Azure DNS Private Resolver is a service that bridges the gap between on-premises DNS and Azure DNS. It facilitates the querying of Azure DNS private zones from on-premises environments and vice versa, eliminating the need for VM-based DNS servers. This service is especially beneficial for hybrid networks, offering a simplified solution for private DNS resolution.
Distributed vs. Centralized DNS Architecture:
- Distributed DNS Architecture: In this setup, a private resolver is located in the hub of a hub-and-spoke VNet topology. The hub VNet is linked to the private DNS zone, enabling resources within the hub to resolve DNS records in the private zone using Azure-provided DNS. The spoke VNet, on the other hand, uses the hub’s inbound endpoint for DNS resolution.
- Centralized DNS Architecture: Here, the spoke VNet sends all its DNS traffic to the inbound endpoint in the Hub VNet. Since the private zone is linked to the Hub VNet, all resources in the Hub, including the inbound endpoint, can resolve the private zone. This means the spoke uses the hub’s inbound endpoint for all DNS resolutions.
How it Works:
- Inbound Endpoints: Think of these as the “receiving end” in Azure. They listen for requests from both Azure and on-site systems. They have their own private address in Azure, and when they get a request, they can find the right address in Azure or on the internet.
- Outbound Endpoints: This is the “sending end” in Azure. If an Azure system needs to find an address that’s on-site or somewhere else, this endpoint sends out the request.
- Forwarding Ruleset: This is like a set of instructions. It tells the outbound endpoint where to send certain requests.
- Forwarding Rules: These are the individual instructions in the ruleset. They say, “For this domain, send the request to this address.”
When and Why to Use It
What’s the Scenario?
- You’re operating in a hybrid environment, combining both on-site systems and Azure cloud services.
- Your on-site systems occasionally need to connect to services in Azure using their domain names, especially when a query doesn’t match a private DNS zone.
Example Situation:
- Let’s say you have an Azure service, like a database in Azure SQL, that’s privately hosted in Azure DNS private zones. Your on-site users wish to connect to this database using its name. The Azure DNS Private Resolver enables you to query Azure services by translating the name into an address that your on-site systems can understand.
- Additionally, if Azure services need to locate something on-site, this tool assists without the need for deploying VM-based DNS servers.
Why Use It?
- Hybrid Environments: It’s tailor-made for scenarios with both on-site and Azure services requiring communication.
- Centralized or Distributed Design: Depending on your Azure virtual network setup, you can centralize all address lookups to one main hub or distribute them across various points using the Azure DNS Private Resolver endpoints and rulesets.
In Practice:
- If your Azure virtual network is set up in a hub-and-spoke design, this tool, with its private resolver architecture, can manage address lookups across the entire design using virtual network links for DNS forwarding rulesets.
- You can even configure the private resolver inbound endpoint IP as custom DNS in a virtual network, directing all DNS queries to the hub VNet in a centralized design. This ensures that if a query doesn’t match a private DNS zone, it can still be resolved without causing a DNS resolution loop.
Technical Insights:
- The private resolver is provisioned within the Azure virtual network, ensuring seamless integration.
- The private resolver is a new service, eliminating the need for custom DNS servers and preventing potential DNS resolution loops.
- It’s designed to work with private zones linked to the private zone, ensuring that Azure services can communicate with on-site systems and vice versa without deploying VM-based DNS servers.
- The service uses DNS servers configured specifically for this purpose, ensuring efficient and accurate name resolution.