CfnTransitGateway

Specifies a transit gateway. You can use a transit gateway to interconnect your virtual private clouds (VPC) and on-premises networks. After the transit gateway enters the `available` state, you can attach your VPCs and VPN connections to the transit gateway. To attach your VPCs, use [AWS::EC2::TransitGatewayAttachment](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-transitgatewayattachment.html) . To attach a VPN connection, use [AWS::EC2::CustomerGateway](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-customer-gateway.html) to create a customer gateway and specify the ID of the customer gateway and the ID of the transit gateway in a call to [AWS::EC2::VPNConnection](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-vpn-connection.html) . When you create a transit gateway, we create a default transit gateway route table and use it as the default association route table and the default propagation route table. You can use [AWS::EC2::TransitGatewayRouteTable](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-transitgatewayroutetable.html) to create additional transit gateway route tables. If you disable automatic route propagation, we do not create a default transit gateway route table. You can use [AWS::EC2::TransitGatewayRouteTablePropagation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-transitgatewayroutetablepropagation.html) to propagate routes from a resource attachment to a transit gateway route table. If you disable automatic associations, you can use [AWS::EC2::TransitGatewayRouteTableAssociation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-transitgatewayroutetableassociation.html) to associate a resource attachment with a transit gateway route table. To create a transit gateway with `EncryptionSupport` enabled through CloudFormation, you will need the `ec2:ModifyTransitGateway` Identity and Access Management (IAM) permission. For more information, see `ModifyTransitGateway` in [Actions, resources, and condition keys for Amazon EC2](https://docs.aws.amazon.com/service-authorization/latest/reference/list_amazonec2.html#amazonec2-actions-as-) of the *Identify and Access Management Service Authorization Reference* .