Use Azure Private Link with Confluent Cloud

Azure Private Link allows for one-way secure connection access from your VNet to Confluent Cloud with an added protection against data exfiltration. This networking option is popular for its unique combination of security and simplicity of setup.

The following diagram summarizes the Azure Private Link architecture between the VNet or subscription and the Confluent Cloud cluster.

To set up to use Azure Private Link with Confluent Cloud:

1. Register your Azure subscription with Confluent Cloud.
2. Create an Azure Private Link connection to Confluent Cloud.
3. Set up DNS records to use Azure Private Endpoints.
4. Validate connectivity to Confluent Cloud.

Requirements and considerations

• Have a Confluent Cloud network (CCN) of type Private Link in Azure available. If a network does not exist, see Confluent Cloud Network on Azure.
• To use an Azure Private Link service with Confluent Cloud, your VNet must allow outbound internet connections for Confluent Cloud Schema Registry, ksqlDB, and Confluent CLI to work.
  • DNS requests to public authority traversing to private DNS zone is required.
  • Confluent Cloud Schema Registry is accessible over the internet.
  • Provisioning new ksqlDB instances requires Internet access. After ksqlDB instances are up and running, they are fully accessible over Azure Private Link connections.
  • Confluent CLI requires internet access to authenticate with the Confluent Cloud control plane.
• Confluent Cloud Console components, such as topic management, need additional configuration to function as they use cluster endpoints. To use all features of the Confluent Cloud Console with Azure Private Link, see Use Confluent Cloud with Private Networking.
• Cross-region Azure Private Link connections are not supported.
• Azure Private Link is only available for use with Dedicated clusters.
• Existing Confluent Cloud clusters cannot be converted to use Azure Private Link.
• Availability zone selection for placement of Confluent Cloud cluster and Azure Private Link service is not supported.

Connectors

Fully-managed Confluent Cloud connectors can connect to data sources or sinks using a public IP address. Sources or sinks in the customer network with private IP addresses are not supported.

Register your Azure subscription with Confluent Cloud

Register your Azure subscription with the Confluent Cloud network for automatic approval of private endpoint connections to the Confluent Cloud network. If required, you can register multiple subscriptions.

Confluent Cloud ConsoleREST API

1. Open the Confluent Cloud Console, in the Network Management tab, click the Confluent Cloud network you want to add the connection to.
2. Click + Private Link Access.
3. Enter the Azure subscription ID for the account containing the VNets you want to make the Azure Private Link connection from. The Azure subscription number can be found on your Azure subscription page of the Azure Portal.
4. Click Save.

Your Azure Private Link connection status will transition from “Pending” to “Active” in the Confluent Cloud Console. You still need to configure the Private Endpoints in your VNet before you can connect to the cluster.

Note the Private Link Service Endpoint to create an Azure Private Link connection from your VNet to the Confluent Cloud cluster. This URL will also be provided later.

Create an Azure Private Link connection to Confluent Cloud

After the connection status is “Active” in the Confluent Cloud Console, configure Private Endpoints in your VNet from the Azure Portal to make the Azure Private Link connection to your Confluent Cloud cluster.

Note

Confluent recommends using a Terraform configuration for setting up Private Link endpoints. This configuration automates the manual steps described below.

For Confluent Cloud single availability zone clusters, create a single Private Endpoint to the Confluent Cloud Service Alias for the Kafka cluster zone.

For Confluent Cloud multi-availability zone clusters, create a Private Endpoint to each of the Confluent Cloud zonal Service Aliases.

To set up the VNet Endpoint for Azure Private Link in your Azure account:

1. In the Confluent Cloud Console in Cluster Overview, gather the following information:

   • In Cluster Settings:

     • Bootstrap server endpoint
     • For single availability zone clusters, the availability zone of the Kafka cluster (Zones in the Cloud details section)

   • In Networking > Details:

     • DNS domain

     • Zonal DNS subdomain

     • Service Aliases

       For single availability zone clusters, you only need the Service Alias of the Kafka cluster zone you retrieved in Cluster Settings above.

2. In the Azure Private Link Center, click Create Private Endpoint.

3. Fill in subscription, resource group, name, and region for the virtual endpoint and click next. The selected subscription must be the same as the one registered with Confluent Cloud.

4. Select the Connect to an Azure resource by resource ID or alias option, paste in the Confluent Cloud Service Alias and click Next. You can find the Confluent Cloud Service Aliases in the Networking tab under Cluster settings in the Confluent Cloud Console.

5. Fill in virtual network and subnet where the Private Endpoint is to be created.

6. Click Review + create. Review the details and click Create to create the Private Endpoint.

7. Wait for the Azure deployment to complete, go to the Private Endpoint resource and verify Private Endpoint connection status is Approved.

Set up DNS records to use Azure Private Endpoints

You must update your DNS records to ensure connectivity passes through Azure Private Link in the supported pattern. Any DNS provider that can ensure DNS is routed as follows is acceptable. Azure Private DNS Zone (used in this example) is one option.

DNS resolution options

For Azure Private Link Confluent Cloud networks, you can use the public or private DNS resolution:

• The private DNS resolution is the recommended option and guarantees fully private DNS resolution.
• The public DNS resolution is useful when you want to ensure that Confluent deployments are homogenous and conform to DNS configurations for your networks.

DNS resolution is selected when you create a Confluent Cloud network, and it cannot be modified after creating the Confluent Cloud network. See Create a Confluent Cloud network.

Public DNS resolution

The public (also known as chased private in Confluent Cloud) DNS resolution is used for the bootstrap server and broker hostnames of a Confluent Cloud cluster that is using Azure Private Link. When the public resolution is used, the clusters in this network requires both public and private DNS to resolve cluster endpoints.

Only the the Confluent Global DNS Resolver (GLB) endpoints are advertised.

The public DNS resolution performs the following two-step process:

1. The Confluent Cloud Global DNS Resolver removes the glb subdomain and returns a CNAME for your bootstrap and broker hostnames.

   Example: $lkc-id-$nid.$region.$cloud.glb.confluent.cloud

   CNAME returned: $lkc-id.$nid.$region.$cloud.confluent.cloud

2. The CNAME resolves to your VNet private endpoints based on the Private DNS Zone configuration.

Warning

Some DNS systems, like Windows DNS service, lack the ability to recursively resolve the previously mentioned two-step process within a single DNS node. To solve the issue, use Private DNS resolution.

Private DNS resolution

When the private DNS resolution is used, the clusters in this network only require private DNS to resolve cluster endpoints. Only non-GLB endpoints are advertised.

Tip

To identity the CNAME DNS zone records to correctly map to zonal endpoints for Confluent Cloud, you can run the DNS helper script.

Configure DNS zones

DNS entries need to be created for Private Link irrespective of the DNS resolution option you selected when creating the Confluent Cloud network.

To update DNS resolution using Azure Private DNS Zone in the Azure console:

1. Create the Private DNS Zone.

   1. Search for the Private DNS Zone resource in the Azure Portal.

   2. Click Add.

   3. Copy the DNS Domain name from the Networking tab under Cluster Settings in the Confluent Cloud Console and use it as the name for the Private DNS Zone.

      For example:

      4kgzg.centralus.azure.confluent.cloud
      

      Note that there is no glb in the DNS Domain name.

      If the Confluent Cloud DNS Domain name includes the logical cluster id which starts with lkc-, omit the logical cluster id when specifying it as the Private DNS Zone name. For example, the DNS Domain name shown as lkc-123abc-4kgzg.centralus.azure.confluent.cloud in Confluent Cloud should be converted to 4kgzg.centralus.azure.confluent.cloud to be used as the Private DNS Zone name.

   4. Fill in subscription, resource group and name and click Review + create.

   5. Wait for the Azure deployment to complete.

2. Create DNS records.

   1. Go to the Private DNS Zone resource as created above.
   2. Click + Record Set.
   3. Create the following record set for Confluent Cloud single availability zone clusters. The IP address of the Private Endpoint can be found under its associated network interface.
      1. Select name as “*”, type as “A”, TTL as “1 Minute” and add IP address of the single virtual endpoint as created above.
   4. Create the following record sets for Confluent Cloud multi-availability zone clusters. The IP address of the Private Endpoint can be found under its associated network interface.
      1. Select name as “*”, type as “A”, TTL as “1 Minute” and add IP addresses of all three virtual endpoints as created above.
      2. Select name as “*.az1”, type as “A”, TTL as “1 Minute” and add IP address of the az1 virtual endpoint as created above.
      3. Select name as “*.az2”, type as “A”, TTL as “1 Minute” and add IP address of the az2 virtual endpoint as created above.
      4. Select name as “*.az3”, type as “A”, TTL as “1 Minute” and add IP address of the az3 virtual endpoint as created above.

3. Attach the Private DNS Zone to the VNets where clients or applications are present.

4. Go to the Private DNS Zone resource and click Virtual network links under settings.

   1. Click Add.
   2. Fill in link name, subscription and virtual network.

Validate connectivity to Confluent Cloud

1. From an instance within the VNet, or anywhere the DNS is set up, run the following to validate Kafka connectivity through Azure Private Link is working correctly.

   1. Set an environment variable with the cluster bootstrap URL.

      export BOOTSTRAP=$<bootstrap-server-url>
      

      The Bootstrap URL displayed in Confluent Cloud Console includes the port (9092). The BOOTSTRAP value should include the full hostname, but do not include the port. This is so that you can run the openssl s_client -connect <host>:<port> command with the required values.

      For example:

      export BOOTSTRAP=lkc-222v1o-4kgzg.centralus.azure.glb.confluent.cloud
      

   2. Test connectivity to your cluster by running the openssl s_client -connect <host>:<port> command, specifying the $BOOTSTRAP environment variable for the <host> value and 9092 for the <port> value.

      openssl s_client -connect $BOOTSTRAP:9092 -servername $BOOTSTRAP -verify_hostname $BOOTSTRAP </dev/null 2>/dev/null | grep -E 'Verify return code|BEGIN CERTIFICATE' | xargs
      

      To run the openssl s_client -connect command, the -connect option requires that you specify the host and the port number. For details, see the openssl documentation for the -connect option option in the openssl s_client documentation.

   3. If the output returned is -----BEGIN CERTIFICATE----- Verify return code: 0 (ok), then connectivity to the bootstrap is confirmed.

      Note

      You might need to update the network security tools and firewalls to allow connectivity. If you have issues connecting after following these steps, confirm which network security systems your organization uses and whether their configurations need to be changed. If you still have issues, run the debug connectivity script and provide the output to Confluent Support for assistance with your Azure Private Link setup.

   4. Log in to the Confluent Cloud CLI with your Confluent Cloud credentials.

      confluent login
      

   5. List the clusters in your organization.

      confluent kafka cluster list
      

   6. Select the cluster with Azure Private Link you wish to test.

      confluent kafka cluster use ...
      

      For example:

      confluent kafka cluster use lkc-222v1o
      

   7. Create a cluster API key to authenticate with the cluster.

      confluent api-key create --resource ... --description ...
      

      For example:

      confluent api-key create --resource lkc-222v1o --description "connectivity test"
      

   8. Select the API key you just created.

      confluent api-key use ... --resource ...
      

      For example:

      confluent api-key use R4XPKKUPLYZSHOAT --resource lkc-222v1o
      

   9. Create a test topic.

      confluent kafka topic create test
      

   10. Start consuming events from the test topic.

       confluent kafka topic consume test
       

   11. Open another terminal tab or window.

   12. Start a producer.

       confluent kafka topic produce test
       

       Type anything into the produce tab and hit Enter; press Ctrl+D or Ctrl+C to stop the producer.

   13. The tab running consume will print what was typed in the tab running produce.

       The cluster is ready for use.

Related content

• For an overview of Azure Private Link, see Setting Up Secure Networking in Confluent with Azure Private Link.

  For getting started with Azure Private Link in Confluent Cloud, you should use the currently supported steps described in this document.