# Associating VPC attachments and subnets with a multicast domain in AWS Transit Gateway
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Use the following procedure to associate a VPC attachment with a multicast domain. When you create an association, you can then select the subnets to include in the multicast domain. 

Before you begin, you must create a VPC attachment on your transit gateway. For more information, see [Amazon VPC attachments in AWS Transit Gateway](tgw-vpc-attachments.md).

**To associate VPC attachments with a multicast domain using the console**

1. Open the Amazon VPC console at [https://console.aws.amazon.com/vpc/](https://console.aws.amazon.com/vpc/).

1. On the navigation pane, choose **Transit Gateway Multicast**.

1. Select the multicast domain, and then choose **Actions**, **Create association**.

1. For **Choose attachment to associate**, select the transit gateway attachment.

1. For **Choose subnets to associate**, select the subnets to include in the multicast domain.

1. Choose **Create association**.

**To associate VPC attachments with a multicast domain using the AWS CLI**  
Use the [associate-transit-gateway-multicast-domain](https://docs.aws.amazon.com/cli/latest/reference/ec2/associate-transit-gateway-multicast-domain.html) command.