Configuring Azure File Sync network endpoints

Azure Files and Azure File Sync provide two main types of endpoints for accessing Azure file shares:

  • Public endpoints, which have a public IP address and can be accessed from anywhere in the world.
  • Private endpoints, which exist within a virtual network and have a private IP address from within the address space of that virtual network.

For both Azure Files and Azure File Sync, the Azure management objects, the storage account and the Storage Sync Service respectively, control both the public and private endpoints. The storage account is a management construct that represents a shared pool of storage in which you can deploy multiple file shares, as well as other storage resources, such as blob containers or queues. The Storage Sync Service is a management construct that represents registered servers, which are Windows file servers with an established trust relationship with Azure File Sync, and sync groups, which define the topology of the sync relationship.

This article focuses on how to configure the networking endpoints for both Azure Files and Azure File Sync. To learn more about how to configure networking endpoints for accessing Azure file shares directly, rather than caching on-premises with Azure File Sync, see Configuring Azure Files network endpoints.

We recommend reading Azure File Sync networking considerations prior to reading this how to guide.

Prerequisites

This article assumes that:

  • You have an Azure subscription. If you don't already have a subscription, then create a free account before you begin.
  • You have already created an Azure file share in a storage account which you would like to connect to from on-premises. To learn how to create an Azure file share, see Create an Azure file share.
  • You allow domain traffic to the following endpoints, see Azure service endpoints:

Additionally:

Create the private endpoints

When you are creating a private endpoint for an Azure resource, the following resources are deployed:

  • A private endpoint: An Azure resource representing either the private endpoint for the storage account or the Storage Sync Service. You can think of this as a resource that connects your Azure resource and a network interface.
  • A network interface (NIC): The network interface that maintains a private IP address within the specified virtual network/subnet. This is the exact same resource that gets deployed when you deploy a virtual machine, however instead of being assigned to a VM, it's owned by the private endpoint.
  • A private DNS zone: If you've never deployed a private endpoint for this virtual network before, a new private DNS zone will be deployed for your virtual network. A DNS A record will also be created for Azure resource in this DNS zone. If you've already deployed a private endpoint in this virtual network, a new A record for Azure resource will be added to the existing DNS zone. Deploying a DNS zone is optional, however highly recommended to simplify the DNS management required.

Note

This article uses the DNS suffixes for the Azure Public regions, core.windows.net for storage accounts and afs.azure.net for Storage Sync Services. This commentary also applies to Azure Sovereign clouds such as the Azure US Government cloud - just substitute the the appropriate suffixes for your environment.

Create the storage account private endpoint

Navigate to the storage account for which you would like to create a private endpoint. In the table of contents for the storage account, select Networking, Private endpoint connections, and then + Private endpoint to create a new private endpoint.

Screenshot of the private endpoint connections item in the storage account table of contents.

The resulting wizard has multiple pages to complete.

In the Basics blade, select the desired subscription, resource group, name, network interface name, and region for your private endpoint. These can be whatever you want, they don't have to match the storage account in any way, although you must create the private endpoint in the same region as the virtual network you wish to create the private endpoint in. Then select Next: Resource.

Screenshot showing how to provide the project and instance details for a new private endpoint.

In the Resource blade, select file for the target sub-resource. Then select Next: Virtual Network.

Screenshot showing how to select which resource you would like to connect to using the new private endpoint.

The Virtual Network blade allows you to select the specific virtual network and subnet you would like to add your private endpoint to. Select dynamic or static IP address allocation for the new private endpoint. If you select static, you'll also need to provide a name and a private IP address. You can also optionally specify an application security group. When you're finished, select Next: DNS.

Screenshot showing how to provide virtual network, subnet, and IP address details for the new private endpoint.

The DNS blade contains the information for integrating your private endpoint with a private DNS zone. Make sure the subscription and resource group are correct, then select Next: Tags.

Screenshot showing how to integrate your private endpoint with a private DNS zone.

You can optionally apply tags to categorize your resources, such as applying the name Environment and the value Test to all testing resources. Enter name/value pairs if desired, and then select Next: Review + create.

Screenshot showing how to optionally tag your private endpoint with name/value pairs for easy categorization.

Click Review + create to create the private endpoint.

If you have a virtual machine inside of your virtual network, or you've configured DNS forwarding as described in Configuring DNS forwarding for Azure Files, you can test that your private endpoint has been set up correctly by running the following commands from PowerShell, the command line, or the terminal (works for Windows, Linux, or macOS). You must replace <storage-account-name> with the appropriate storage account name:

nslookup <storage-account-name>.file.core.windows.net

If everything has worked successfully, you should see the following output, where 192.168.0.5 is the private IP address of the private endpoint in your virtual network (output shown for Windows):

Server:  UnKnown
Address:  10.2.4.4

Non-authoritative answer:
Name:    storageaccount.privatelink.file.core.windows.net
Address:  192.168.0.5
Aliases:  storageaccount.file.core.windows.net

Create the Storage Sync Service private endpoint

Navigate to the Private Link Center by typing Private Link into the search bar at the top of the Azure portal. In the table of contents for the Private Link Center, select Private endpoints, and then + Add to create a new private endpoint.

A screenshot of the private link center

The resulting wizard has multiple pages to complete.

In the Basics blade, select the desired resource group, name, and region for your private endpoint. These can be whatever you want, they don't have to match the Storage Sync Service in any way, although you must create the private endpoint in the same region as the virtual network you wish to create the private endpoint in.

A screenshot of the Basics section of the create private endpoint section

In the Resource blade, select the radio button for Connect to an Azure resource in my directory. Under the Resource type, select Microsoft.StorageSync/storageSyncServices for the resource type.

The Configuration blade allows you to select the specific virtual network and subnet you would like to add your private endpoint to. Select the same virtual network as the one you used for the storage account above. The Configuration blade also contains the information for creating/updating the private DNS zone.

Click Review + create to create the private endpoint.

You can test that your private endpoint has been set up correctly by running the following commands from PowerShell.

$privateEndpointResourceGroupName = "<your-private-endpoint-resource-group>"
$privateEndpointName = "<your-private-endpoint-name>"

Get-AzPrivateEndpoint `
        -ResourceGroupName $privateEndpointResourceGroupName `
        -Name $privateEndpointName `
        -ErrorAction Stop | `
    Select-Object -ExpandProperty NetworkInterfaces | `
    Select-Object -ExpandProperty Id | `
    ForEach-Object { Get-AzNetworkInterface -ResourceId $_ } | `
    Select-Object -ExpandProperty IpConfigurations | `
    Select-Object -ExpandProperty PrivateLinkConnectionProperties | `
    Select-Object -ExpandProperty Fqdns | `
    ForEach-Object { Resolve-DnsName -Name $_ } | `
    Format-List

If everything has worked correctly, you should see the following output where 192.168.1.4, 192.168.1.5, 192.168.1.6, and 192.168.1.7 are the private IP addresses assigned to the private endpoint:

Name     : mysssmanagement.westus2.afs.azure.net
Type     : CNAME
TTL      : 60
Section  : Answer
NameHost : mysssmanagement.westus2.privatelink.afs.azure.net


Name       : mysssmanagement.westus2.privatelink.afs.azure.net
QueryType  : A
TTL        : 60
Section    : Answer
IP4Address : 192.168.1.4

Name     : myssssyncp.westus2.afs.azure.net
Type     : CNAME
TTL      : 60
Section  : Answer
NameHost : myssssyncp.westus2.privatelink.afs.azure.net


Name       : myssssyncp.westus2.privatelink.afs.azure.net
QueryType  : A
TTL        : 60
Section    : Answer
IP4Address : 192.168.1.5

Name     : myssssyncs.westus2.afs.azure.net
Type     : CNAME
TTL      : 60
Section  : Answer
NameHost : myssssyncs.westus2.privatelink.afs.azure.net


Name       : myssssyncs.westus2.privatelink.afs.azure.net
QueryType  : A
TTL        : 60
Section    : Answer
IP4Address : 192.168.1.6

Name     : mysssmonitoring.westus2.afs.azure.net
Type     : CNAME
TTL      : 60
Section  : Answer
NameHost : mysssmonitoring.westus2.privatelink.afs.azure.net


Name       : mysssmonitoring.westus2.privatelink.afs.azure.net
QueryType  : A
TTL        : 60
Section    : Answer
IP4Address : 192.168.1.7

Restrict access to the public endpoints

You can restrict access to the public endpoints of both the storage account and the Storage Sync Services. Restrict access to the public endpoint provides additional security by ensuring that network packets are only accepted from approved locations.

Restrict access to the storage account public endpoint

Access restriction to the public endpoint is done using the storage account firewall settings. In general, most firewall policies for a storage account will restrict networking access to one or more virtual networks. There are two approaches to restricting access to a storage account to a virtual network:

  • Create one or more private endpoints for the storage account and disable access to the public endpoint. This ensures that only traffic originating from within the desired virtual networks can access the Azure file shares within the storage account.
  • Restrict the public endpoint to one or more virtual networks. This works by using a capability of the virtual network called service endpoints. When you restrict the traffic to a storage account via a service endpoint, you are still accessing the storage account via the public IP address.

Note

The Allow Azure services on the trusted services list to access this storage account exception must be selected on your storage account to allow trusted first party Microsoft services such as Azure File Sync to access the storage account. To learn more, see Grant access to trusted Azure services.

Grant access to trusted Azure services and disable access to the storage account public endpoint

When access to the public endpoint is disabled, the storage account can still be accessed through its private endpoints. Otherwise valid requests to the storage account's public endpoint will be rejected.

Navigate to the storage account for which you would like to restrict all access to the public endpoint. In the table of contents for the storage account, select Networking.

At the top of the page, select the Enabled from selected virtual networks and IP addresses radio button. This will un-hide a number of settings for controlling the restriction of the public endpoint. Select Allow Azure services on the trusted services list to access this storage account to allow trusted first party Microsoft services such as Azure File Sync to access the storage account.

Screenshot of the Networking blade with the required settings to disable access to the storage account public endpoint.

Grant access to trusted Azure services and restrict access to the storage account public endpoint to specific virtual networks

When you restrict the storage account to specific virtual networks, you are allowing requests to the public endpoint from within the specified virtual networks. This works by using a capability of the virtual network called service endpoints. This can be used with or without private endpoints.

Navigate to the storage account for which you would like to restrict the public endpoint to specific virtual networks. In the table of contents for the storage account, select Networking.

At the top of the page, select the Enabled from selected virtual networks and IP addresses radio button. This will un-hide a number of settings for controlling the restriction of the public endpoint. Select +Add existing virtual network to select the specific virtual network that should be allowed to access the storage account via the public endpoint. Select a virtual network and a subnet for that virtual network, and then select Enable.

Select Allow Azure services on the trusted services list to access this storage account to allow trusted first party Microsoft services such as Azure File Sync to access the storage account.

Screenshot of the Networking blade with a specific virtual network allowed to access the storage account via the public endpoint.

Disable access to the Storage Sync Service public endpoint

Azure File Sync enables you to restrict access to specific virtual networks through private endpoints only; Azure File Sync does not support service endpoints for restricting access to the public endpoint to specific virtual networks. This means that the two states for the Storage Sync Service's public endpoint are enabled and disabled.

This is not possible through the Azure portal. Please select the Azure PowerShell tab to get instructions on how to disable the Storage Sync Service public endpoint.

Azure Policy

Azure Policy helps enforce organization standards and assess compliance against those standards at scale. Azure Files and Azure File Sync expose several useful audit and remediation network policies that help you monitor and automate your deployment.

Policies audit your environment and alert you if your storage accounts or Storage Sync Services diverge from the defined behavior. For example, if a public endpoint is enabled when your policy was set to have the public endpoints disabled. Modify/deploy policies take things a step further and proactively modify a resource (such as the Storage Sync Service) or deploy resources (such as private endpoints), to align with the policies.

The following pre-defined policies are available for Azure Files and Azure File Sync:

Action Service Condition Policy name
Audit Azure Files The storage account's public endpoint is enabled. See Grant access to trusted Azure services and disable access to the storage account public endpoint for more information. Storage accounts should restrict network access
Audit Azure File Sync The Storage Sync Service's public endpoint is enabled. See Disable access to the Storage Sync Service public endpoint for more information. Public network access should be disabled for Azure File Sync
Audit Azure Files The storage account needs at least one private endpoint. See Create the storage account private endpoint for more information. Storage account should use a private link connection
Audit Azure File Sync The Storage Sync Service needs at least one private endpoint. See Create the Storage Sync Service private endpoint for more information. Azure File Sync should use private link
Modify Azure File Sync Disable the Storage Sync Service's public endpoint. Modify - Configure Azure File Sync to disable public network access
Deploy Azure File Sync Deploy a private endpoint for the Storage Sync Service. Configure Azure File Sync with private endpoints
Deploy Azure File Sync Deploy an A record to privatelink.afs.azure.net DNS zone. Configure Azure File Sync to use private DNS zones

Set up a private endpoint deployment policy

To set up a private endpoint deployment policy, go to the Azure portal, and search for Policy. The Azure Policy center should be a top result. Navigate to Authoring > Definitions in the Policy center's table of contents. The resulting Definitions pane contains the pre-defined policies across all Azure services. To find the specific policy, select the Storage category in the category filter, or search for Configure Azure File Sync with private endpoints. Select ... and Assign to create a new policy from the definition.

The Basics blade of the Assign policy wizard enables you to set a scope, resource or resource group exclusion list, and to give your policy a friendly name to help you distinguish it. You don't need to modify these for the policy to work, but you can if you want to make modifications. Select Next to advance to the Parameters page.

On the Parameters blade, select the ... next to the privateEndpointSubnetId drop down list to select the virtual network and subnet where the private endpoints for your Storage Sync Service resources should be deployed. The resulting wizard may take several seconds to load the available virtual networks in your subscription. Select the appropriate virtual network/subnet for your environment and click Select. Select Next to advance to the Remediation blade.

In order for the private endpoint to be deployed when a Storage Sync Service without a private endpoint is identified, you must select the Create a remediation task on the Remediation page. Finally, select Review + create to review the policy assignment and Create to create it.

The resulting policy assignment will be executed on a periodic basis and may not run immediately after being created.

See also