Azure DNS

As organizations increasingly shift to the cloud, managing domain names and DNS records through scalable, secure, and integrated services becomes critical. Azure DNS, part of Microsoft Azure's suite of services, enables you to host your domain name system (DNS) domains in Azure. It supports both public and private DNS zones and provides a highly available and performant infrastructure for DNS management.

In this article, we walk through the core concepts of Azure DNS, including how to identify and verify domains, create and delegate DNS zones, add DNS records, and plan for private DNS environments.

A. Identify Domains and Custom Domains

When setting up an identity infrastructure using Microsoft Entra ID (formerly Azure Active Directory), domains play a central role.

1. Default Domain Creation

When a new Entra ID tenant is created, Azure automatically provisions a default domain name in the format:

CopyEdityourdomain.onmicrosoft.com

This default domain enables immediate use of Azure services but may not reflect your organization’s brand.

2. Customizing Domain Names

Organizations typically add their own custom domain names (e.g., contoso.com) to ensure brand consistency and usability across services like Microsoft 365, custom applications, and directory synchronization.

3. Domain Name Verification

Once a custom domain is added, Azure requires verification to ensure the organization owns the domain. This is a crucial security step that prevents unauthorized use of a domain.

B. Verify Custom Domain Names

Verifying a custom domain confirms your organization's ownership and allows integration with Azure services.

1. Ownership Demonstration

Verification involves adding a special DNS record to your domain’s DNS zone. This process prevents malicious actors from registering domains they do not own.

2. Adding DNS Records

Azure provides a DNS record—usually a TXT or MX type. This record must be added to your domain’s existing DNS zone (hosted with your DNS provider, if not Azure).

For example, a TXT record might look like:

makefileCopyEditName: @
Type: TXT
Value: MS=msXXXXXXXX

3. Verification Query

After the record is added, Azure performs a DNS lookup. It queries the domain for the presence of the provided record. If found and valid, the domain is marked as verified.

C. Create Azure DNS Zones

A DNS zone is an administrative space that holds DNS records for a domain. In Azure DNS, creating zones is foundational for managing your public or private domain infrastructure.

1. Hosting DNS Records

Each DNS zone in Azure DNS contains resource record sets (RR sets), which define how DNS queries are resolved for that domain.

2. Zone Name Uniqueness

If multiple zones have the same domain name (e.g., in different subscriptions or regions), Azure assigns unique name server (NS) addresses to each instance. This ensures proper domain resolution and avoids conflicts.

3. Root Domain Registration

The parent domain (like contoso.com) must be registered with a domain registrar and configured to use the Azure-provided name servers. This step points internet traffic to Azure DNS for resolution.

D. Delegate DNS Domains

Delegation allows Azure DNS to manage specific parts of your domain hierarchy, including subdomains or entire domains.

1. Azure DNS Name Servers

When creating a DNS zone in Azure, it provides four name server (NS) addresses. These must all be used when updating the registrar or parent domain to ensure reliability and redundancy.

2. Updating the Registrar

After creating the DNS zone in Azure, go to your domain registrar and update the domain’s NS records with those from Azure. This delegates DNS authority to Azure.

3. Delegating Child Zones

For subdomains (e.g., dev.contoso.com), you must register NS records in the parent zone. This process ensures that DNS queries for the child zone are directed to the appropriate Azure DNS servers.

E. Add DNS Record Sets

Managing DNS effectively in Azure involves working with record sets, which are collections of similar records in a DNS zone.

1. Definition of a Record Set

A record set groups DNS records of the same type and name (e.g., multiple A records for www.contoso.com). This helps organize and simplify DNS management.

2. Record Limits

Each record set can contain up to 20 individual records. This is particularly useful for scenarios like load balancing across multiple IP addresses.

3. Record Constraints

You cannot add identical records (same name and type with the same data) within a set, as this would create ambiguity in DNS responses.

4. Record Type Selection

Changing the record type (A, AAAA, CNAME, MX, etc.) in the Azure portal dynamically updates the input fields required, ensuring users provide relevant data for that record type.

F. Plan for Private DNS Zones

Azure also supports Private DNS Zones, which provide internal name resolution for virtual networks (VNets) without exposing DNS records to the internet.

1. Custom Internal Domains

With private DNS, you can define your own custom internal domain names such as internal.contoso.com.

2. Name Resolution Across VNets

Private DNS zones can be linked to one or more VNets, providing seamless name resolution for virtual machines (VMs) within and across networks.

3. Automatic Record Management

Azure can automatically manage hostname-to-IP mappings for VMs, reducing the need for manual DNS updates.

4. Eliminating Custom Solutions

By using Azure Private DNS, organizations eliminate the need for custom DNS infrastructure, such as maintaining on-premises DNS servers or third-party services.

5. Full Record Type Support

Private DNS zones in Azure support all common DNS record types (A, AAAA, CNAME, MX, PTR, etc.), making them a robust choice for enterprise environments.

Conclusion

Azure DNS provides a powerful, scalable, and secure way to manage DNS records for both public and private domains. Whether you're onboarding a new custom domain, setting up internal name resolution, or integrating with Entra ID, understanding the mechanics of Azure DNS zones, record sets, and delegation is key to maintaining a reliable and efficient network infrastructure.

By adopting these best practices and capabilities, organizations can simplify their DNS management and enhance both availability and security within the Azure ecosystem.

About me: I am a Cloud Architect who like to learn and write about Cloud concepts. If you are an organization that want to hire me then I can be contacted at techonlinewriter@gmail.com

Mastering Azure DNS: Domain Management and Configuration Best Practices

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