How can I use Bicep to create an Azure DNS alias record?

Question

We use Bicep to manage our DNS records in an Azure DNS Zone.

I have recently set up an Azure Front Door profile with custom domains, which is working fine. One of the custom domains is an apex domain, so the Azure portal creates a DNS A record (in alias mode) which points to the Azure resource: i.e. the Front Door profile/endpoint.

The portal provides a nice UI to manage this. Because we manage our DNS using Bicep, we now need to add this A record definition to our Bicep file to avoid accidentally reverting it in future Bicep deployments.

I can find no documentation on how to do this. I have tried something like this:

resource aliasRecord 'Microsoft.Network/dnsZones/A@2018-05-01' = {
  parent: dnsZone
  name: '@'
  properties: {
    TTL: 3600
    targetResource: {
      id: '/subscriptions/{guid}/resourcegroups/{rgName}/providers/Microsoft.Network/frontdoors/{profileName}/frontendendpoints/{endpointName}'
    }
  }
} 

I get a "Reference records are not supported for resource" error. I can't find any guidance on how to reference the Front Door endpoint here.

Is there any documentation or advice on how to represent a DNS alias record like this in Bicep?

Answer 1

Hello James Munro,

I could not find a doc for you on this, but as a suggestion, you could export the ARM from the resource on the portal them decompile to bicep.
In the Azure Portal, go to the Resource groups section and select the resource group containing your DNS records. Then export https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/export-template-cli

You can then proceed to decompile using:

https://learn.microsoft.com/en-us/azure/azure-resource-manager/bicep/decompile?tabs=azure-cli

This will give you the code you need

You can mark it 'Accept Answer' and 'Upvote' if this helped you

Regards,

Abiola

Answer 2

I followed Abiola's useful advice and copied the resource template for the DNS zone, and decompiled it ("paste as Bicep" in VS Code).

The resulting Bicep looks something like this:

resource aliasRecord 'Microsoft.Network/dnsZones/A@2018-05-01' = {
  parent: dnsZone
  name: '@'
  properties: {
    TTL: 3600
    targetResource: {
      id: '/subscriptions/{guid}/resourceGroups/{rgName}/providers/Microsoft.Cdn/profiles/{frontDoorName}/afdendpoints/{endpointName}'
    }
  }
}

So I was close, with a couple of incorrect route segments in my first attempt. Note that the endpointName is only the part you define, not the random part added by AFD.

I have tested this Bicep and it worked perfectly.

Thanks Abiola!