1. Tenancy, Compartments, and VCNs

Your tenancy is your company’s root account. Inside it, create compartments—logical containers for isolation, access control, and cost tracking.

DMCloudArchitect (Tenancy) ├─ Production │ ├─ Networking │ ├─ Compute │ └─ Databases └─ Development ├─ Networking ├─ Compute └─ Databases 

Keep network resources in a dedicated Networking compartment for clean IAM and troubleshooting.

2. What Is a VCN?

A VCN is a private, customizable network in a single region that can span multiple ADs. You define IP ranges (CIDRs), subnets, gateways, routes, and security.

• Example VCN CIDR: 10.0.0.0/16
• Example Subnets: 10.0.1.0/24 (public), 10.0.2.0/24 (private)

3. Public vs Private Subnets

Public Subnets

• Internet access via an Internet Gateway.
• For web frontends, bastions, public LBs.
• Instances can have public IPs.

Private Subnets

• No direct internet exposure.
• For databases and internal services.
• Outbound only via NAT Gateway for updates.

4. Create a Basic Network (Console)

1. Create a Compartment: Identity & Security → Compartments → Create.
2. Create a VCN: Networking → Virtual Cloud Networks → Create (Quick setup or Custom). Choose CIDR like 10.0.0.0/16.
3. Create Subnets: Public-Subnet 10.0.1.0/24, Private-Subnet 10.0.2.0/24.
4. Configure Routes: Public → 0.0.0.0/0 → Internet Gateway; Private → 0.0.0.0/0 → NAT Gateway.
5. Security: Use NSGs or Security Lists. Example: allow TCP 22 (SSH) from your IP to public; allow DB port from app subnet only.

5. Key Networking Components

• Internet Gateway: public ingress/egress
• NAT Gateway: private egress only
• Service Gateway: private access to OCI services
• DRG: on-prem/VPN or inter-VCN connectivity
• LPG: local peering same region
• Route Tables: traffic paths per subnet
• NSGs/Security Lists: firewall policies

6. Organizing for Growth

• Plan non-overlapping CIDRs for future peering/VPNs.
• Use tags for owner/cost center.
• Separate prod vs dev in distinct compartments/VCNs.
• Document the IP plan early.

VCN: 10.0.0.0/16 ├─ Public Subnet: 10.0.1.0/24 (Web) └─ Private Subnet: 10.0.2.0/24 (DB)

7. Tips for Developers & Small Businesses

• Start with Quick Create; customize later.
• Keep most resources private; expose only what’s needed.
• Automate with Terraform/CLI for repeatability.
• Use Flow Logs and Monitoring for troubleshooting.

8. Summary

Organize with compartments, define a clean VCN, split public/private subnets, and apply least-privilege security. A solid network unlocks secure, scalable deployments for your workloads.