The image shows the Primary OCI Region - US West (Phoenix) IP address 10.0.0.0/16 which hosts a Production VCN and a Pre-Production VCN 10.1.0.0/16 and the Oracle Services Network (OSN). Each VCN uses the service gateway to connect to Object Storage in the Oracle Services Network (OSN).
The Production VCN hosts a public subnet with two app servers and a private subnet with two app servers.
The Pre-Production VCN hosts a private subnet with two app servers.
The Production VCN uses the Internet Gateway to connect to the internet and send and receive traffic.
The Pre-Production VCN uses the NAT Gateway to send outbound data to the internet.
The VCNs use the DRG to connec to the On-Premises Data Center using Site-to-Site VCN or FastConnect.