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

Question

We use Bicep to manage our DNS records.

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 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 need to add this A record definition to our Bicep file to avoid accidentally reverting it in future 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.

Azure DNS alias records can only point to the Front Door profile, not a specific frontend endpoint—use a CNAME for subdomains (sub.example.com) or alias A for apex (example.com), but referencing individual frontend endpoints is not supported @jamesfm — Vinay B
– Vinay B, Commented Mar 7 at 7:23
Hi Vinay, are you sure? In the Azure portal for the DNS A (alias) record I am able to select from a list of the endpoints on each front door profile. Do you have any documentation on this point? — jamesfm
– jamesfm, Commented Mar 7 at 9:36
could you share a screenshot the dns configuration from azure portal? — Thomas
– Thomas, Commented Mar 8 at 3:50

jamesfm · Accepted Answer · 2025-03-08 21:46:39Z

0

After a day, I asked this same question on MS Q&A. The helpful answer was to:

copy the json template for the DNS zone
decompile it into Bicep and see how the alias A record is created

I did this and it revealed the errors in my target resource id, which should have been:

'/subscriptions/{guid}/resourceGroups/{rgName}/providers/Microsoft.Cdn/profiles/{frontDoorName}/afdendpoints/{endpointName}'

Once I tried it with this syntax it worked fine.

A useful approach when you can't find any documentation! See also:

https://learn.microsoft.com/en-us/answers/questions/2202284/how-can-i-use-bicep-to-create-an-azure-dns-alias-r

answered Mar 8 at 21:46

jamesfm

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