Use AWS Transit Gateway on Confluent Cloud

You can use AWS Transit Gateway to simplify the peering architecture. The Transit Gateway acts as a highly scalable cloud router. Rather than peering VPCs directly to each other, you only have to set up a Transit Gateway attachment between the Transit Gateway and your VPC once, and you can access all the networks connected to the Transit Gateway.

With Transit Gateways, your data is encrypted and never travels over the internet.

Requirements and considerations

To use AWS Transit Gateway with Confluent Cloud, you need the followings:

Add an AWS Transit Gateway connection

To create an AWS Transit Gateway:

  1. In AWS, use an existing Transit Gateway, or create a Transit Gateway.

  2. In Confluent Cloud, add a Transit Gateway attachment.

  3. In AWS, accept the Transit Gateway attachment.

    This step can be automated by selecting the Auto accept shared attachments option when you create the Transit Gateway in the first step.

  4. In AWS, update the route table.

    AWS automatically adds the new Transit Gateway attachment to the default Transit Gateway route table.

Add an AWS Transit Gateway in AWS

  1. In Confluent Cloud Console, in the Network management tab for your environment, click the Transit Gateway network resource to retrieve the Confluent Cloud AWS Account ID of the network resource you want to use.

  2. In the Amazon VPC console, add an AWS Transit Gateway for your AWS account. For details, see Create a Transit Gateway.

    • Select the Auto accept shared attachments option.

  3. In AWS Resource Access Manager (RAM) Console, create a resource share for your Confluent Cloud network.

    For details, see Creating a resource share in AWS RAM and Share a Transit Gateway in the AWS documentation.

    Use the Confluent Cloud AWS Account ID you retrieved in the first step as the principal of the resource share in the Principals step.

    In Confluent Cloud, it is not possible to share the same RAM resources between Organizations, due to security concerns.

    To use a Transit Gateway across two Confluent Cloud organizations, you need to create a new RAM share for the same Transit Gateway and use it for the second organization.

  4. Save the Amazon Resource Name (ARN) of the resource share.

    You need to provide the name when you create a Transit Gateway attachment.

Add an AWS Transit Gateway attachment in Confluent Cloud

Add a Transit Gateway attachment in Confluent Cloud.

  1. In the Confluent Cloud Console, select your environment, and click Network management.

  2. In the Network management tab, select the AWS Transit Gateway network resource that you want to add a Transit Gateway attachment to, and click the Connections tab.

  3. Click + Transit Gateway. The Add Transit Gateway Attachment page appears.

  4. Specify the following information, and click Add.

    • Name: Enter a name for your attachment.

    • AWS RAM Share ARN: Use the ARN you saved in the last step of creating a resource share in AWS.

    • AWS Transit Gateway ID: The identifier (ID) of the AWS Transit Gateway that you are connecting to the Confluent Cloud network.

    • AWS VPC CIDR: A comma-separated list of destination CIDRs that you want to route to from the Confluent Cloud network when you attach Confluent Cloud to your Transit Gateway.

      This field needs to contain all CIDR blocks in your network (cloud VPC, on-prem) that needs return routes from the Confluent Cloud network via the Transit Gateway attachment.

      The RFC 1918 and RFC 6598 private address ranges are supported as described in Confluent Cloud network CIDR blocks and block size for peering and Transit Gateway.

      Public IP address ranges are not allowed.

      The routes should not be identical and not completely within the Confluent Cloud network CIDRs. For example, with the Confluent Cloud network CIDR of 10.0.0.0/16, 10.0.0.0/8 is a valid Transit Gateway route, but 10.0.0.0/24 is not a valid route.

  5. Your Transit Gateway Attachment will transition to READY in the Confluent Cloud Console.

    You may need to check if Auto accept shared attachments is configured on your Transit Gateway on AWS.


If your Transit Gateway attachment fails, delete the attachment and create a new one.

Attachment failures can occur for the following reasons:

  • The attachment is not shared with the correct AWS principal for the Confluent Cloud network.

    Even if the auto-accept all attachment option is turned on, you still need to add the Confluent Cloud AWS Account ID to the AWS resource share you create in Add an AWS Transit Gateway in AWS.

  • The Transit Gateway was not added to the AWS resource share.

  • The AWS resource share ARN is not correct.

If you delete the Transit Gateway attachment, you must also delete the transit gateway route table entry for the Confluent Cloud network.

Accept the Transit Gateway attachment in AWS

This step can be automated by selecting the Auto accept shared attachments option when you create the Transit Gateway in the first step.

When the connection status is “Pending” in the Confluent Cloud Console, go to the Amazon VPC Console and accept the peering request.

  1. In the Amazon VPC Console, click Transit gateway attachments in the navigation pane.

  2. Select the pending Transit Gateway attachment (the status is Pending).

  3. Click Actions, and click Accept request.

  4. When prompted for confirmation, choose Accept request.

    Save the Transit Gateway attachment id. The value is prefixed with tgw-attach-. You need to input this value in the next step when you add the attachment to the route table.

When the connection request is accepted, the connection status becomes “Ready” in the Confluent Cloud Console.

Add the Transit Gateway route to the AWS Transit Gateway route table

AWS automatically adds the new Transit Gateway attachment to the default Transit Gateway route table, and these steps might not be necessary for your AWS account.

In AWS, add the Confluent Cloud CIDR to the route table with the target of your AWS Transit Gateway.

For the routing to become effective, the route table must be associated with subnet(s).

  1. Go to the Amazon VPC Console, and click Transit gateway route tables under Transit gateways navigation section.

  2. Click the Transit Gateway route table for your VPC.

  3. Click Create static route, and specify the following.

    Add routes for all three /27 CIDR blocks to all your VPC route tables, not just the zone-aligned routes.

    • CIDR: Specify the Confluent Cloud network VPC CIDR block.

      You can find the Confluent Cloud network VPC CIDR block in the Network Overview of your Confluent Cloud network, in the Confluent Cloud CIDR field.

    • Type: Select Active.

    • Choose attachment:

      Select the Transit Gateway attachment ID that corresponds to the transit gateway attachment you created in Add an AWS Transit Gateway attachment in Confluent Cloud. You can find the corresponding attachment ID in the Transit gateway attachments page.

  4. Click Create static route.

For details, see Update AWS Transit Gateway route table.

Migrate from AWS VPC peering connections to AWS Transit Gateway attachments

Warning

When you migrate from VPC peering to a Transit Gateway, you cannot add the exact same CIDR route on the Transit Gateway as the CIDR that is used in your VPC peering connection.

To migrate from a Confluent Cloud network that uses AWS VPC Peering to a network using an AWS Transit Gateway hub, perform the following steps:

  1. Establish a maintenance window.

    Maintaining concurrent Transit Gateway attachments and VPC peering connections might result in a degraded experience due to asymmetric routing with MTU mismatches between the two connectivity types. Confluent recommends establishing a planned “maintenance window” during which both connection types exist to avoid packet losses for your critical workloads. While concurrent connections exist, traffic will be charged at AWS transit gateway rates.

  2. File a Confluent Support ticket.

    Because of the potential for degraded experience, migrations between VPC peering connections and Transit Gateway attachments on the same network require filing a Confluent Support ticket.

    Sign in to the Confluent Support Portal at https://support.confluent.io/hc/, click SUBMIT A REQUEST, and then click AWS Transit Gateway Provisioning.

    • Request to migrate your Confluent Cloud VPC Peering network (with existing VPC peering connections) to an AWS Transit Gateway network.
    • Include your Confluent Cloud network name and network ID (available from the Confluent Cloud Console).

  3. After Confluent Support temporarily enables concurrent connection types (for both VPC peering connections and Transit Gateway attachments), you will be informed that you can proceed with your migration, and you can continue to the next step.

  4. For each existing VPC peering connection, perform the following steps:

    1. In AWS, create a Transit Gateway.

    2. In Confluent Cloud, add a Transit Gateway attachment.

    3. In the Amazon VPC console, update the AWS VPC route table.

      Edit the target of the associated routes to direct traffic to the transit gateway instead of the peering connection.

    4. In the Confluent Cloud Console, delete the existing VPC peering connection.

    5. In the AWS VPC console, verify that the AWS peering resource are deleted.

    Warning

    If your VPC resources are not deleted, asymmetric routing and packet losses occur, resulting in a degraded experience.

  5. Validate connectivity over the newly provisioned resources.

  6. After you complete the migration and validation steps, inform Confluent Support so that they can disable VPC peering connections and close the ticket.

Configure DNS forwarding

To resolve hostnames that reside within private DNS zones or a self-hosted DNS server and access your own VPC or on-prem from Confluent Cloud, set up DNS forwarding in Confluent Cloud.

For example, you can use DNS forwarding for Confluent Cloud fully-managed connectors that need to access data in your VPC.

DNS forwarding requires VPC peering or TGW connection where there is bi-directional network access between your network and Confluent Cloud clusters.

Step 1: Get DNS resolver IP addresses

To use the DNS forwarding feature with your AWS VPC, you can set up AWS Inbound Endpoints or use your own DNS server:

  • If you wish to forward DNS requests from Confluent Cloud to a Route53 hosted zone, create Inbound Endpoints for Confluent Cloud network to access your DNS servers.

    AWS recommends deploying multiple endpoints in different availability zones for availability reasons.

    For details, see Configuring inbound endpoints.

    Once the endpoints are created, as described in the next step, in Confluent Cloud, input the IP addresses of the Inbound Endpoints to which to forward requests.

  • If you want to use your self-hosted DNS server, use the IP address of that DNS server in Confluent Cloud in the next step.

Step 2: Create a DNS Forwarder in Confluent Cloud

Set up DNS forwarding in Confluent Cloud:

  1. In Confluent Cloud, navigate to the DNS Forwarding tab on the Network Detail page.
  2. Input the following information:
    • DNS server IPs: Up to 3 IP addresses of your DNS servers to which we should forward DNS requests.
    • Domain list: Up to 10 domains to which you wish to route the DNS requests.
  3. Wait until provisioning is complete and DNS is propagated.

Next steps