Create AWS Direct Connect gateway (DXGW) “X” and assign a unique autonomous system number (ASN). Attach the Private Virtual Interface (VIF) to DXGW X. Create DXGW “Y” and assign a unique ASN. Attach the Transit VIF to DXGW Y. Create a Virtual Private Gateway (VGW) and attach to DXGW X. Assign a unique ASN to VGW. Attach the VGW to VPC A. Create a AWS Transit Gateway (TGW) and attach to DXGW Y using DXGW attachment, and to VPC A using VPC A attachment, respectively. Create a parent subnet (10.0.0.0/24) with Amazon Elastic Compute Cloud (Amazon EC2) instance B in an Availability Zone (AZ1) and associate it with a route table. Create another subnet (10.0.1.0/24) in the AWS Local Zone (LZ) where the latency sensitive app will be running (EC2 instance A). Associate this to a separate LZ route table. Add the the AZ1 parent subnet (10.0.0.0/24) in in the DXGW Y “Allowed Prefixes” list. The AZ1 parent subnet (10.0.0.0/24) is advertised using TGW and DXGW Y back to on-premises. Trafficdestined to the parent subnet (routes that fall inside /24) follow the TGW path. Any traffic destined to the Local Zone subnet (10.0.1.0/24) follow a shorter VGW path, without hairpinning through the Local Zone’s parent Region (routes that fall outside /24). We don’t recommend any resource accessing the local zone subnet from on-premises through Transit Gateway, as traffic using this path would hairpin through the parent Region.
