How to dynamically resolve resource name by using Alias record in Azure

Alias records in Azure DNS allow DNS names to point directly to Azure resources, such as Azure public IPs, Traffic Manager profiles, or Azure Content Delivery Network (CDN) endpoints.

They dynamically resolve to the current IP address or endpoint of the target resource, eliminating the need to manually update DNS records when the resource’s IP address changes.

Key Features of Alias Records

1. Dynamic Resolution: Automatically resolves to the current IP or endpoint.

2. No Extra Costs: Azure charges only for DNS queries; no additional cost for alias records.

3. Simplifies Management: Avoids the need to manually manage changes in IPs.

Example Scenario

You have a web application hosted on an Azure App Service or behind an Azure Public IP, and you want to dynamically resolve its DNS name without manual updates.

Steps to Create and Use Alias Records

1. Prerequisites

1. An Azure DNS zone (e.g., example.com).

2. A resource that supports alias records:

   • Azure Public IP address

   • Traffic Manager profile

   • Azure Front Door or CDN endpoint

2. Create a Public IP or Target Resource

If you don't already have a resource to point to, create one. For example:

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az network public-ip create \
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--name MyPublicIP \
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--resource-group MyResourceGroup \
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--allocation-method Static

3. Create an Alias Record Using Azure CLI

To create an alias record that resolves to the public IP:

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az network dns record-set a add-alias \
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--resource-group MyResourceGroup \
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--zone-name example.com \
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--record-set-name www \
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--alias-type azureResource \
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--target-resource-id $(az network public-ip show \
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                      --name MyPublicIP \
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                      --resource-group MyResourceGroup \
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                      --query id -o tsv)

Explanation of Parameters:

• --zone-name: The DNS zone name (e.g., example.com).

• --record-set-name: The subdomain (e.g., www for www.example.com).

• --alias-type: Specifies the target resource type (azureResource).

• --target-resource-id: The resource ID of the Azure public IP or other resource.

4. Verify the Alias Record

Check the record details:

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az network dns record-set a show \
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--resource-group MyResourceGroup \
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--zone-name example.com \
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--name www

You should see a reference to the target resource (MyPublicIP) instead of an IP address.

Creating Alias Records in the Azure Portal

1. Go to Azure DNS Zones in the Azure Portal.

2. Select your DNS zone (e.g., example.com).

3. Click + Record set.

4. Choose the record type (e.g., A record).

5. Check Alias record set.

6. Select the target resource (e.g., a Public IP or Traffic Manager profile).

7. Save the record.

Advanced Scenarios

1. Alias Record for Traffic Manager

If you’re using Azure Traffic Manager for load balancing:

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az network dns record-set a add-alias \
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--resource-group MyResourceGroup \
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--zone-name example.com \
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--record-set-name traffic \
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--alias-type azureResource \
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--target-resource-id $(az network traffic-manager profile show \
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                      --name MyTrafficProfile \
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                      --resource-group MyResourceGroup \
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                      --query id -o tsv)

2. Alias Record for CDN

For Azure CDN:

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az network dns record-set cname add-alias \
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--resource-group MyResourceGroup \
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--zone-name example.com \
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--record-set-name cdn \
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--alias-type azureResource \
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--target-resource-id $(az cdn endpoint show \
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                    --name MyCDNEndpoint \
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                    --resource-group MyResourceGroup \
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                    --query id -o tsv)

Benefits of Using Alias Records

1. Dynamic Updates: No need to update DNS records when the IP or endpoint changes.

2. Integration with Azure Resources: Automatically tracks changes to Azure resources.

3. Resilience: Ensures minimal downtime during updates or migrations.

Verification

1. Use a DNS lookup tool (nslookup or dig) to verify:

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nslookup www.example.com

2. Ensure the name resolves to the current IP or endpoint of the target resource.

Next Steps

• Monitor DNS Queries: Use Azure Monitor to track DNS queries for your alias records.

• Integrate with Automation: Automate the creation of alias records in CI/CD pipelines for dynamic deployments.

Let me know if you'd like assistance with a specific resource type or deeper automation use cases.