A company has two business units (BUs). The company operates in the us-east-1 Region and the us-west-1 Region. The company plans to extend to more Regions in the future. Each BU has a VPC in each…

Creating a new Transit Gateway for each new BU in each Region and peering them leads to a complex, unscalable, and difficult-to-manage N-squared peering mesh as the number of BUs and Regions grows, which is inefficient.

While AWS Cloud WAN is the right service, configuring a *single segment for all business units* would prevent the company from isolating some BUs from others, directly failing a key requirement.

AWS Cloud WAN provides a highly scalable and operationally efficient solution for global networks. Configuring a core network with edge locations in both Regions and dedicating a separate segment for each business unit allows for clear logical isolation. The core network policy then centrally defines and controls traffic flow and isolation rules between these segments, accommodating future BUs and Regions with ease and meeting the isolation requirement.

Attaching new VPCs to existing Transit Gateways and managing isolation purely through TGW route tables becomes increasingly complex and less operationally efficient as the number of BUs, VPCs, and Regions increases, especially when granular isolation rules are needed across regions.