Cloudflare's Internal DNS: Architecture and Design for Private Networks

Introduction to Cloudflare Internal DNS

Cloudflare's Internal DNS is designed to provide authoritative and recursive DNS capabilities specifically for private networks. It consolidates management of both public and private DNS records into a unified control plane, accessible via a single API, offering centralized audit trails and policy management. This approach aims to reduce operational complexity for IT teams dealing with large internal network infrastructures, particularly those with complex split-horizon DNS requirements.

Architectural Components

The service is built upon two core components leveraging Cloudflare's decade-long experience in operating large-scale DNS infrastructure:

• Gateway Resolver: This component is responsible for evaluating incoming DNS requests against registered policies (e.g., block or forward) and routing them. It acts as the initial point of contact for internal queries.
• Internal Authoritative DNS: This component stores and resolves authoritative records for private resources such as internal applications, service endpoints, and databases. It handles the actual resolution when a request is forwarded by the Gateway Resolver.

Operational Entities and Workflow

Users interact with three key entities to configure and manage their internal DNS:

• Internal Zones: These contain the specific authoritative records for private resources within an organization's network.
• DNS Views: Allow the composition of multiple internal zones for distinct use cases, enabling complex split-horizon setups without needing separate parallel systems and minimizing configuration duplication.
• Resolver Policies: Stored within the Gateway Resolver, these policies dictate how incoming DNS requests are handled. They can block requests, forward them to a specific DNS View for internal resolution, or route them to the public path if no internal match is found. DNS Views can also be configured to fall back to public resolution for names not found internally.

Comparison with Other Cloud Providers

While Cloudflare offers this integrated solution, other major cloud providers like AWS (Route 53 Resolver, private hosted zones), Azure (Private DNS, DNS Private Resolver), and Google Cloud (private, forwarding, peering zones in Cloud DNS) provide similar capabilities for managing private and public DNS registries within their respective ecosystems. Cloudflare's offering stands out by providing a unified platform across different cloud environments or on-premise infrastructure via its network edge.