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Unlike Virtual Private Gateways, TGW Attachments connect to specific subnets in a VPC. We will be making these TGW Attachments to multiple private the utility subnets in your VPCs. For best resiliency, we will select private subnets in multiple Availability Zones (AZs) for the TGW Attachments. In most Cornell AWS accounts, each private subnet resides in a unique AZ. If your VPC contains more than one private subnet in a given AZ, we will consult with AWS account owners to determine the best private subnet to select for the TGW Attachments. This is because each AZ can accommodate exactly one TGW Attachment.VPCs which were specifically created for this purpose.
TGW Attachments will be created during the Migration phase of the migration. See Migration Process.
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