This image shows an Oracle Cloud Infrastructure region with a single availability domain and 3 fault domains. The region provides a single virtual cloud network (VCN).

The VCN provides an internet gateway and 4 regional public subnets arranged as functional tiers. Each subnet provides a route table and a security list.

• Bastion Host Tier - regional public subnet: A bastion host node resides in fault domain 2 and validates traffic from the internet gateway.

• Load Balancing Tier regional public subnet: Active (fault domain 1) and standby (fault domain 2) load balancers manage traffic to the Tomcat application server VMs.

• Application Tier - regional private subnet: Tomcat server VMs reside in fault domains 1 and 2.

• Database Tier - regional private subnet: MySQL Database Service system includes a primary database in fault domain 1 and secondary databases in fault domains 2 and 3.