A company is designing its network configuration in the AWS Cloud. The company uses AWS Organizations to manage a multi-account setup. The company has three OUs. Each OU contains more than 100 AWS accounts. Each account has a single VPC, and all the VPCs in each OU are in the same AWS Region. The CIDR ranges for all the AWS accounts do not overlap. The company needs to implement a solution in which VPCs in the same OU can communicate with each other but cannot communicate with VPCs in other OUs. Which solution will meet these requirements with the LEAST operational overhead?