A company has multiple business units that each have separate accounts on AWS.

Instruct each business unit to add a unique secondary CIDR range to the business unit's VPC. Peer the VPCs and use a private NAT gateway in the secondary range to route traffic to the marketing team.

Create an Amazon EC2 instance to serve as a virtual appliance in the marketing account's VPC. Create an AWS Site-to-Site VPN connection between the marketing team and each business unit's VPC. Perform NAT where necessary.

Create an AWS PrivateLink endpoint service to share the marketing application. Grant permission to specific AWS accounts to connect to the service. Create interface VPC endpoints in other accounts to access the application by using private IP addresses.

Create a Network Load Balancer (NLB) in front of the marketing application in a private subnet. Create an API Gateway API. Use the Amazon API Gateway private integration to connect the API to the NLB. Activate IAM authorization for the API. Grant access to the accounts of the other business units.