This image shows the east-west traffic flow from the web or application to the database in a regional hub and spoke topology that uses a Cisco Threat Defense firewall.

It includes three virtual cloud networks (VCNs):

• Hub VCN (192.168.0.0/16): The hub VCN houses the Cisco Threat Defense firewall. The inside subnet uses Gig0/0 for internal traffic to or from the Cisco Threat Defense firewall. The hub VCN communicates with spoke VCNs through dynamic routing gateway.
• Web or application tier spoke VCN (10.0.0.0/24): The VCN contains a single subnet. An application load balancer manages traffic to the web or application VMs. The application tier VCN is connected to the hub VCN over dynamic routing gateway.
• Database tier spoke VCN (10.0.1.0/24): The VCN contains a single subnet that contains the primary database system. The database tier VCN is connected to the hub VCN over dynamic routing gateway.

East-west traffic flow from the web or application to the database:

1. Traffic that moves from the web or application tier to the database tier (10.0.1.10) is routed through the web or application subnet route table (destination 0.0.0.0/0).
2. Traffic moves from the web or application subnet route table to the DRG for the database tier spoke VCN.
3. Traffic moves from the DRG through the hub VCN Ingress route table to the Cisco Threat Defense firewall VMs using internal network load balancer. Network load balancer has more than one backends pointing to inside interfaces (Gig0/0) of VM Series firewall.
4. Traffic from the Cisco Threat Defense firewall is routed through the inside subnet route table (destination: 10.0.1.0/24).
5. Traffic moves from the inside subnet route table to the DRG for the database spoke VCN.
6. Traffic moves from the DRG for the database system through database spoke VCN attachment.