Use private endpoints for Managed Prometheus and Azure Monitor workspace

Use private endpoints for Managed Prometheus and your Azure Monitor workspace to allow clients on a virtual network (VNet) to securely query data over a Private Link. The private endpoint uses a separate IP address within the VNet address space of your Azure Monitor workspace resource. Network traffic between the clients on the VNet and the workspace resource traverses the VNet and a private link on the Microsoft backbone network, eliminating exposure from the public internet.

Using private endpoints for your workspace enables you to:

• Secure your workspace by configuring the public access network setting to block all connections on the public query endpoint for the workspace.
• Increase security for the VNet, by enabling you to block exfiltration of data from the VNet.
• Securely connect to workspaces from on-premises networks that connect to the VNet using VPN or ExpressRoutes with private-peering.

Conceptual overview

A private endpoint is a special network interface for an Azure service in your Virtual Network (VNet). When you create a private endpoint for your workspace, it provides secure connectivity between clients on your VNet and your workspace. The private endpoint is assigned an IP address from the IP address range of your VNet. The connection between the private endpoint and the workspace uses a secure private link.

Applications in the VNet can connect to the workspace over the private endpoint seamlessly, using the same connection strings and authorization mechanisms that they would use otherwise.

Private endpoints can be created in subnets that use Service Endpoints. Clients in the subnet can then connect to a workspace using a private endpoint, while using service endpoints to access other services.

When you create a private endpoint for a workspace in your VNet, a consent request is sent for approval to the workspace account owner. If the user requesting the creation of the private endpoint is also an owner of the workspace, this consent request is automatically approved.

Azure Monitor workspace owners can manage consent requests and the private endpoints through the 'Private Access' tab on the Networking page for the workspace in the Azure portal.

Create a private endpoint

To create a private endpoint by using the Azure portal, PowerShell, or the Azure CLI, see the following articles. The articles feature an Azure web app as the target service, but the steps to create a private link are the same for an Azure Monitor workspace.

When you create a private endpoint, make the following selections from the dropdown lists on the basic tab:

• Resource type - Select Microsoft.Monitor/accounts. Specify the Azure Monitor workspace to which it connects.
• Target sub-resource - Select prometheusMetrics .

Create a private endpoint using the following articles:

• Create a private endpoint using Azure portal

• Create a private endpoint using Azure CLI

• Create a private endpoint using Azure PowerShell

Connect to a private endpoint

Clients on a VNet using the private endpoint should use the same query endpoint for the Azure monitor workspace as clients connecting to the public endpoint. We rely upon DNS resolution to automatically route the connections from the VNet to the workspace over a private link.

By default, We create a private DNS zone attached to the VNet with the necessary updates for the private endpoints. However, if you're using your own DNS server, you may need to make additional changes to your DNS configuration. The section on DNS changes below describes the updates required for private endpoints.

DNS changes for private endpoints

When you create a private endpoint, the DNS CNAME resource record for the workspace is updated to an alias in a subdomain with the prefix privatelink. By default, we also create a private DNS zone, corresponding to the privatelink subdomain, with the DNS A resource records for the private endpoints.

When you resolve the query endpoint URL from outside the VNet with the private endpoint, it resolves to the public endpoint of the workspace. When resolved from the VNet hosting the private endpoint, the query endpoint URL resolves to the private endpoint's IP address.

For the example below we're using k8s02-workspace located in the China North region. The resource name isn't guaranteed to be unique, which requires us to add a few characters after the name to make the URL path unique; for example, k8s02-workspace-<key>. This unique query endpoint is shown on the Azure Monitor workspace Overview page.

The DNS resource records for the Azure Monitor workspace when resolved from outside the VNet hosting the private endpoint, are:

Name	Type	Value
k8s02-workspace-<key>.<region>.prometheus.monitor.azure.cn	CNAME	k8s02-workspace-<key>.privatelink.<region>.prometheus.monitor.azure.cn
k8s02-workspace-<key>.privatelink.<region>.prometheus.monitor.azure.cn	CNAME	<AMW regional service public endpoint>
<AMW regional service public endpoint>	A	<AMW regional service public IP address>

As previously mentioned, you can deny or control access for clients outside the VNet through the public endpoint using the 'Public Access' tab on the Networking page of your workspace.

The DNS resource records for 'k8s02-workspace' when resolved by a client in the VNet hosting the private endpoint, are:

Name	Type	Value
k8s02-workspace-<key>.<region>.prometheus.monitor.azure.cn	CNAME	k8s02-workspace-<key>.privatelink.<region>.prometheus.monitor.azure.cn
k8s02-workspace-<key>.privatelink.<region>.prometheus.monitor.azure.cn	A	<Private endpoint IP address>

This approach enables access to the workspace using the same query endpoint for clients on the VNet hosting the private endpoints, as well as clients outside the VNet.

If you're using a custom DNS server on your network, clients must be able to resolve the FQDN for the workspace query endpoint to the private endpoint IP address. You should configure your DNS server to delegate your private link subdomain to the private DNS zone for the VNet, or configure the A records for k8s02-workspace with the private endpoint IP address.

The recommended DNS zone names for private endpoints for an Azure Monitor workspace are:

Resource	Target sub-resource	Zone name
Azure Monitor workspace	prometheusMetrics	privatelink.<region>.prometheus.monitor.azure.cn

For more information on configuring your own DNS server to support private endpoints, see the following articles:

• Name resolution for resources in Azure virtual networks
• DNS configuration for private endpoints

Pricing

For pricing details, see Azure Private Link pricing.

Known issues

Keep in mind the following known issues about private endpoints for Azure Monitor workspace.

Workspace query access constraints for clients in VNets with private endpoints

Clients in VNets with existing private endpoints face constraints when accessing other Azure Monitor workspaces that have private endpoints. For example, suppose a VNet N1 has a private endpoint for a workspace A1. If workspace A2 has a private endpoint in a VNet N2, then clients in VNet N1 must also query workspace data in account A2 using a private endpoint. If workspace A2 doesn't have any private endpoints configured, then clients in VNet N1 can query data from that workspace without a private endpoint.

This constraint is a result of the DNS changes made when workspace A2 creates a private endpoint.

Next steps

• Managed Grafana network settings
• Azure Private Endpoint DNS configuration