Azure Private DNS policies with Azure AI services

Question

Azure Private DNS policies with Azure AI services

Martin Pelikan 20

We implemented automatic registration of DNS records of Azure Private Links as recommended by Azure https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/ready/azure-best-practices/private-link-and-dns-integration-at-scale.

This works great for most cases, but Azure AI Services. Let's say I create Azure AI Foundry (the same case will be for Azure OpenAI Instance). During or upon creation, I can create a Private Endpoint. This private endpoint is always a subresource of type "account", and if you use the Azure Portal, it will offer an integration with the Azure Private DNS Zone "privatelink.aiservices.azure.com". The Private Endpoint itself will have a Network Interface with three IPs:

privateEndpointIpConfig.abcdef123456

IPv4

Primary

10.0.0.1 (Dynamic)

-

privateEndpointIpConfig.ghijkl123456

IPv4

Secondary

10.0.0.2 (Dynamic)

-

privateEndpointIpConfig.mnopqr123456

IPv4

Secondary

10.0.0.3 (Dynamic)

DNS configuration of the PE will then show three different records:
Customer Visible FQDNs for the Network Interface:

10.0.0.1

test-ai-foundry-00001.cognitiveservices.azure.com

10.0.0.2

test-ai-foundry-00001.openai.azure.com

10.0.0.3

test-ai-foundry-00001.services.ai.azure.com

And Azure Private DNS Zone will have the following record:
10.0.0.1 test-ai-foundry-00001.privatelink.aiservices.azure.com

The A-record provided by Azure Private DNS Zone does not work for accessing the AI Foundry via its private endpoint. Instead, the AI Foundry uses services.ai.azure.com.

My question: How can I use Azure policies from the initial link to automatically add a correct DNS record in the Private DNS Zone? When is which zone used? And why is aiservices.azure.com, created automatically during PE creation, not in the list of DNS zones for Azure AI Services?

Private DNS zone domains for AI Services:

Azure AI services (Microsoft.CognitiveServices/accounts)accountprivatelink.cognitiveservices.azure.com privatelink.openai.azure.com privatelink.services.ai.azure.comcognitiveservices.azure.com openai.azure.com services.ai.azure.com

santoshkc 15,615 Reputation points Microsoft External Staff Moderator

2025-05-28T16:29:56.2966667+00:00
Hi @Martin Pelikan,

A -Records are normally list of private Ips of all dependent resources mentioned in DNS config.

It has only put one IP in the A -record

10.0.0.1 test-ai-foundry-00001.privatelink.aiservices.azure.com

So,You have to add all private Ips along their FQDN names in DNS zone. So would suggest to manually create the A-records in DNS zone

For Custom DNS server setup, we should create conditional forwarder to forward the queries to Azure DNS resolver as per C-records and host names.

Policy can only help you enforce choosing a correct region or DNS zone here.

Attached relevant documentation from AI foundry hub on using private links and managed virtual network.

https://learn.microsoft.com/en-us/azure/ai-foundry/how-to/configure-private-link?tabs=azure-portal&pivots=fdp-project (For Own Vnet using Bastion or VPN gateway or Express route) .

How to configure a managed network for a hub - Azure AI Foundry | Microsoft Learn (managed vnet along your own vnet).

Anamoly found in our Repro

found at our side is amlworkspace while at yours it is showing account FQDNS look like workspace.westus.api.azureml.ms and westus.notebooks.azure.net.

Here are answer to your other queries.

1. How can I use Azure policies to automatically add a correct DNS record in the Private DNS Zone?

Azure does not currently support automatic DNS record creation via Azure Policy for services like Azure AI Services. However, there are a few mechanisms to manage DNS records:

Auto registration is available for virtual machines only. When a virtual network is linked to a private DNS zone with auto registration enabled, DNS A records are automatically created for VMs. This does not apply to PaaS services like Azure AI Services [1].

For Azure Private Endpoints, DNS records are automatically created in the linked private DNS zone when the private endpoint is created. This is handled by the Azure platform, not by Azure Policy [2].

If you need to enforce the presence of specific DNS zones or validate configurations, you can use Azure Policy to audit or deny resource deployments based on DNS zone linkage, but not to create DNS records.

2. When is which DNS zone used?

The DNS zone used depends on the Azure service and the region. For Azure AI Services:

The expected DNS zone for private endpoints is typically:

privatelink.<service>.azure.com

For example, for Azure AI Services, it might be:

privatelink.api.azureml.ms privatelink.notebooks.azure.net

You must manually create or link the correct private DNS zone to your virtual network. Azure provides a reference list of DNS zone names per service [2].

If you use a custom DNS server, you must ensure that it forwards requests for these zones to Azure’s DNS or resolves them appropriately [3].

Why is aiservices.azure.com, created automatically during PE creation, not in the list of DNS zones for Azure AI Services?

The zone aiservices.azure.com is not officially documented in the list of private DNS zones for Azure AI Services [2].

It may be created automatically by Azure during private endpoint provisioning for certain AI services, especially those under the AI Foundry or newer Azure AI offerings.

This discrepancy likely arises from internal service naming or preview features not yet reflected in public documentation. Microsoft may be consolidating or evolving service endpoints under aiservices.azure.com.

If this zone appears in your environment, it is safe to assume it is required for resolution of the specific AI service you are using. You should ensure it is properly linked to your virtual network.

Note:

Saying all that Suggesting you refer official Azure Foundry hub virtual network documentation for automatic DNS registration and A record creation and configure conditional forwarder and A records in Host server (from Hub network) to avoid hassle of manually creating the DNS zones and modifying A records

References

[1] What is autoregistration feature in Azure DNS private zones?

[2] Azure Private Endpoint private DNS zone values | Microsoft Learn

[3] Networking recommendations for AI workloads on Azure

[4] Configure Virtual Networks for Azure AI services - Azure AI services [5] https://learn.microsoft.com/en-us/azure/ai-foundry/how-to/configure-private-link?tabs=azure-portal&pivots=fdp-project

[6] - Custom DNS server in AI/ML (for a more clearer picture of Custom DNS scenario)

I hope this helps.

Thank you.
Martin Pelikan 20 Reputation points

2025-05-29T06:28:51.6966667+00:00

Thank you for the elaborate answer. This does not support the design proposed by Azure and linked earlier: https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/ready/azure-best-practices/private-link-and-dns-integration-at-scale.

The idea is that each new Private Endpoint is not linked to any Azure Private DNS Zone during its creation. Azure Policy identifies a new PE without a link to an Azure Private DNS Zone and creates the link to the corresponding zone itself. This is done by identifying what Resource and Subresource type the PE is.

In case of Azure AI Services, this is impossible to gauge since both Azure Open AI and Azure AI Foundry (and probably other AI-related services) use a type Microsoft.CognitiveServices/accounts. Plus, the Private Endpoint uses three domain names

cognitiveservices.azure.com
openai.azure.com
services.ai.azure.com
plus undocumented aiservices.azure.com.

Let's say we build some very custom and very clever automation. Should we add only primary IP, or are secondary IPs (10.0.0.2 and 10.0.0.3) used?

Are there alternative ways to achieve it without adding records into Private DNS Zones manually? We specifically used the proposed solution to avoid any manual actions.

Are there services like Azure AI Services that can't be applied to the recommended Azure design?
Manas R Mohanty 17,270 Reputation points Moderator

2025-05-30T15:55:08.4866667+00:00

Hi Martin Pelikan

Thank you connecting and providing more details on your custom policy requirements

We are reviewing with policy team and sync with you once we get an update from them.

Thank you.
Manas R Mohanty 17,270 Reputation points Moderator

2025-06-04T21:19:47+00:00

Hi Martin Pelikan

Sorry for the delay in response.

We have already forwarded this query to our Service Area Lead after reviewing with concerned team on policy and pushing for product team attention on the clarification.

Appreciate your patience on this matter.

Thank you.

Navneet Verma 0

Hi, I have faced similar issue. We can identify the Azure AI Foundry/Azure AI services using .kind='AIServices'. Also the workaround is to add additional policy for azure aiservices along with this policy https://www.azadvertizer.net/azpolicyadvertizer/5d34e716-cc45-4649-8a05-f1f7deaf2f36.html, you also have to edit some condition to this existing policy so that both policy won't clash.

{ 
  "type": "Microsoft.Authorization/policyDefinitions",
  "name": "Cogn-AIService-DNS-Zone",
  "properties": {
    "displayName": "Configure Cognitive AI Services accounts to use private DNS zones",
    "policyType": "Custom",
    "mode": "Indexed",
    "description": "Use private DNS zones to override the DNS resolution for a private endpoint. A private DNS zone links to your virtual network to resolve to Cognitive Services accounts.",
    "metadata": {
      "category": "Cognitive Services",
      "version": "1.0.0"
    },
    "version": "1.0.0",
    "parameters": {
      "aiservicesPrivateDnsZoneId": {
        "type": "String",
        "metadata": {
          "displayName": "AIservices Private DNS Zone ID",
          "description": "The Private DNS Zone ID for Azure AIservices resources.",
          "strongType": "Microsoft.Network/privateDnsZones",
          "assignPermissions": true
        }
      },
      "cognitivePrivateDnsZoneId": {
        "type": "String",
        "metadata": {
          "displayName": "Default Private DNS Zone ID",
          "description": "The Private DNS Zone ID for Azure Cognitive Services resources.",
          "strongType": "Microsoft.Network/privateDnsZones",
          "assignPermissions": true
        }
      },
      "openaiPrivateDnsZoneId": {
        "type": "String",
        "metadata": {
          "displayName": "OpenAI Private DNS Zone ID",
          "description": "The Private DNS Zone ID for Azure OpenAI resources.",
          "strongType": "Microsoft.Network/privateDnsZones",
          "assignPermissions": true
        }
      }
    },
    "policyRule": {
      "if": {
        "allOf": [
          {
            "equals": "Microsoft.Network/privateEndpoints",
            "field": "type"
          },
          {
            "count": {
              "field": "Microsoft.Network/privateEndpoints/privateLinkServiceConnections[*]",
              "where": {
                "allOf": [
                  {
                    "contains": "Microsoft.CognitiveServices/accounts",
                    "field": "Microsoft.Network/privateEndpoints/privateLinkServiceConnections[*].privateLinkServiceId"
                  },
                  {
                    "equals": "account",
                    "field": "Microsoft.Network/privateEndpoints/privateLinkServiceConnections[*].groupIds[*]"
                  }
                ]
              }
            },
            "greaterOrEquals": 1
          }
        ]
      },
      "then": {
        "details": {
          "deployment": {
            "properties": {
              "mode": "incremental",
              "parameters": {
                "aiservicesPrivateDnsZoneId": {
                  "value": "[parameters('aiservicesPrivateDnsZoneId')]"
                },
                "cognitivePrivateDnsZoneId": {
                  "value": "[parameters('cognitivePrivateDnsZoneId')]"
                },
                "location": {
                  "value": "[field('location')]"
                },
                "openaiPrivateDnsZoneId": {
                  "value": "[parameters('openaiPrivateDnsZoneId')]"
                },
                "privateEndpointName": {
                  "value": "[field('name')]"
                },
                "privateLinkServiceId": {
                  "value": "[field('Microsoft.Network/privateEndpoints/privateLinkServiceConnections[*].privateLinkServiceId')]"
                }
              },
              "template": {
                "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
                "contentVersion": "1.0.0.0",
                "parameters": {
                  "aiservicesPrivateDnsZoneId": {
                    "type": "string"
                  },
                  "cognitivePrivateDnsZoneId": {
                    "type": "string"
                  },
                  "location": {
                    "type": "string"
                  },
                  "openaiPrivateDnsZoneId": {
                    "type": "string"
                  },
                  "privateEndpointName": {
                    "type": "string"
                  },
                  "privateLinkServiceId": {
                    "type": "array"
                  }
                },
                "resources": [
                  {
                    "apiVersion": "2022-07-01",
                    "location": "[parameters('location')]",
                    "name": "[concat(parameters('privateEndpointName'), '/deployedByPolicy')]",
                    "properties": {
                      "privateDnsZoneConfigs": [
                        {
                          "name": "openai-private-dns-zone",
                          "properties": {
                            "privateDnsZoneId": "[if(equals(reference(parameters('privateLinkServiceId')[0], '2022-12-01', 'Full').kind, 'AIServices'), parameters('openaiPrivateDnsZoneId'), json('null'))]"
                          }
                        },
                        {
                          "name": "aiservices-private-dns-zone",
                          "properties": {
                            "privateDnsZoneId": "[if(equals(reference(parameters('privateLinkServiceId')[0], '2022-12-01', 'Full').kind, 'AIServices'), parameters('aiservicesPrivateDnsZoneId'), json('null'))]"
                          }
                        },
                        {
                          "name": "cognitive-private-dns-zone",
                          "properties": {
                            "privateDnsZoneId": "[if(equals(reference(parameters('privateLinkServiceId')[0], '2022-12-01', 'Full').kind, 'AIServices'), parameters('cognitivePrivateDnsZoneId'), json('null'))]"
                          }
                        }
                      ]
                    },
                    "type": "Microsoft.Network/privateEndpoints/privateDnsZoneGroups"
                  }
                ]
              }
            }
          },
          "roleDefinitionIds": [
            "/providers/Microsoft.Authorization/roleDefinitions/4d97b98b-1d4f-4787-a291-c67834d212e7",
            "/providers/Microsoft.Authorization/roleDefinitions/acdd72a7-3385-48ef-bd42-f606fba81ae7"
          ],
          "type": "Microsoft.Network/privateEndpoints/privateDnsZoneGroups"
        },
        "effect": "deployIfNotExists"
      }
    },
    "versions": [
      "1.0.0"
    ]
  }
}

Changes in existing policy

"properties": {
                      "privateDnsZoneConfigs": [
                        {
                          "name": "account-private-dns-zone",
                          "properties": {
                            "privateDnsZoneId": "[if(equals(reference(parameters('privateLinkServiceId')[0], '2022-12-01', 'Full').kind, 'AIServices'), json('null'), if(equals(reference(parameters('privateLinkServiceId')[0], '2022-12-01', 'Full').kind, 'OpenAI'), parameters('openaiPrivateDnsZoneId'), parameters('defaultPrivateDnsZoneId')))]"
                          }
                        }
                      ]
                    }

Manas R Mohanty 17,270 Reputation points Moderator

2025-06-05T23:39:06.5333333+00:00

Hey Navneet Verma

Thank you for sharing your observation.

Martin Pelikan Could you please see if the additional policy and properties in above comment helps address your issue.

Your answer

Martin Pelikan 20 Reputation points

2025-05-29T06:28:51.6966667+00:00

Thank you for the elaborate answer. This does not support the design proposed by Azure and linked earlier: https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/ready/azure-best-practices/private-link-and-dns-integration-at-scale.

The idea is that each new Private Endpoint is not linked to any Azure Private DNS Zone during its creation. Azure Policy identifies a new PE without a link to an Azure Private DNS Zone and creates the link to the corresponding zone itself. This is done by identifying what Resource and Subresource type the PE is.

In case of Azure AI Services, this is impossible to gauge since both Azure Open AI and Azure AI Foundry (and probably other AI-related services) use a type Microsoft.CognitiveServices/accounts. Plus, the Private Endpoint uses three domain names

cognitiveservices.azure.com
openai.azure.com
services.ai.azure.com
plus undocumented aiservices.azure.com.

Let's say we build some very custom and very clever automation. Should we add only primary IP, or are secondary IPs (10.0.0.2 and 10.0.0.3) used?

Are there alternative ways to achieve it without adding records into Private DNS Zones manually? We specifically used the proposed solution to avoid any manual actions.

Are there services like Azure AI Services that can't be applied to the recommended Azure design?
Manas R Mohanty 17,270 Reputation points Moderator

2025-05-30T15:55:08.4866667+00:00

Hi Martin Pelikan

Thank you connecting and providing more details on your custom policy requirements

We are reviewing with policy team and sync with you once we get an update from them.

Thank you.
Manas R Mohanty 17,270 Reputation points Moderator

2025-06-04T21:19:47+00:00

Hi Martin Pelikan

Sorry for the delay in response.

We have already forwarded this query to our Service Area Lead after reviewing with concerned team on policy and pushing for product team attention on the clarification.

Appreciate your patience on this matter.

Thank you.
Manas R Mohanty 17,270 Reputation points Moderator

2025-06-05T23:39:06.5333333+00:00

Hey Navneet Verma

Thank you for sharing your observation.

Martin Pelikan Could you please see if the additional policy and properties in above comment helps address your issue.