Azure Networking

Azure DNS Private Resolver Overview

Azure DNS Private Resolver is a cloud-native, recursive DNS resolver service that you can use to resolve DNS queries for your virtual networks (VNets). It allows you to define DNS forwarding rulesets that enable conditional forwarding of DNS queries to custom DNS servers and to on-premises DNS servers through VPN or Azure ExpressRoute.

Key Benefits

• Simplified DNS Management: Consolidate your DNS resolution logic in a central service, reducing the need for managing multiple DNS servers within each VNet.
• Hybrid Cloud Connectivity: Seamlessly resolve names for both Azure resources and on-premises resources by forwarding queries to your existing DNS infrastructure.
• Enhanced Security: Avoid exposing your on-premises DNS servers directly to the internet. Resolver endpoints provide a secure gateway for DNS queries.
• Scalability and High Availability: As a managed Azure service, it offers built-in scalability and high availability, ensuring your DNS resolution remains robust.
• Cost-Effective: Reduce the operational overhead and infrastructure costs associated with deploying and managing your own DNS servers.

How it Works

Azure DNS Private Resolver operates by using inbound endpoints and outbound endpoints, combined with DNS forwarding rulesets.

Endpoints

• Inbound Endpoint: Allows DNS queries from your virtual networks to be sent to the DNS Private Resolver. Resources in your VNets are configured to use the IP addresses of the inbound endpoint as their DNS servers.
• Outbound Endpoint: Enables DNS queries to be forwarded from the DNS Private Resolver to other DNS servers. These can be custom DNS servers within Azure or on-premises DNS servers.

DNS Forwarding Rulesets

A DNS forwarding ruleset associates a set of DNS forwarding rules with specific virtual networks. Each rule specifies a condition (e.g., a domain suffix) and an action (e.g., forward to a specific IP address).

When a DNS query arrives at an inbound endpoint:

1. The resolver checks the associated forwarding ruleset for matching rules based on the queried domain.
2. If a rule matches, the query is forwarded to the specified target DNS server(s) via an outbound endpoint.
3. If no rule matches, the query is resolved using Azure DNS private zones associated with the VNet or by forwarding to Azure DNS.

Common Use Cases

Key Concepts

• DNS Zones: Azure DNS private zones that host private domain records for your VNets.
• DNS Forwarder: A mechanism within the resolver to forward queries to other DNS servers.
• Rules: Define the logic for forwarding DNS queries based on domain names.