Securing Your OCI Network: Practical Best Practices for Every Deployment

December 09, 2025 Mariusz Antonik Networking 3 min read 513 views

1. Introduction

In this guide, I’ll show you how to secure your Oracle Cloud network with the same approach I use in production customer environments. OCI offers enterprise-grade networking features—if configured properly.

Security starts with the network. And in OCI, that means controlling access with VCNs, subnets, security lists, NSGs, IAM, gateways, and monitoring.

2. What Problem This Solves

Most tenants are exposed because:

0.0.0.0/0 is allowed everywhere
Unnecessary public IPs
No segmentation between app and DB layers
No egress control
No flow logs or monitoring enabled
IAM policies too broad

This guide eliminates those risks.

3. Step-by-Step Guide

Step 1 — Lock Down SSH

Never allow:

Instead use:

your office IP
VPN
Bastion service

Step 2 — Replace Security Lists with NSGs

Network Security Groups allow instance-level control, not subnet-level.

Create NSG:

Add ingress rule:

Step 3 — Use Private Subnets Everywhere

Public subnet = only for:

Load balancers
Bastion host (if not using OCI Bastion)

App and DB should ALWAYS be private.

Step 4 — Enable VCN Flow Logs

Use for:

blocked traffic troubleshooting
security audits

Step 5 — Configure IAM the Right Way

Never assign Administrators group to developers.

Follow least privilege:

network admins → manage virtual-network-family
db admins → manage database-family
devs → manage instance-family

Example policy:

4. Architecture Diagram

              Internet
                 │
      ┌───────────────────────┐
      │ Public LB (NSG:443)   │
      └───────────────────────┘
                 │
─────────────────┼──────────────────────
           Private App Subnet
       ┌─────────────────────────┐
       │ App Servers (NSG:80)    │
       └─────────────────────────┘
                 │
─────────────────┼──────────────────────
            Private DB Subnet
      ┌────────────────────────┐
      │ MySQL / ATP (Port 3306)│
      └────────────────────────┘
                 │
          Service Gateway

5. Best Practices

Use NSGs per tier: web, app, db
Use Vault for secrets, not environment variables
Disable unused protocols (ICMP, UDP)
Use IPSec VPN or FastConnect for enterprise workloads
Add alarms (port scans, unusual traffic)

6. Common Errors / Troubleshooting

Problem	Cause	Resolution
App can't reach DB	NSG blocking	Add DB port in NSG
Slow traffic	Wrong MTU	Set MTU 1500 or test jumbo frames
Outbound internet blocked	Missing NAT route	Fix route table
Policy denied	Wrong IAM	Update group policy

7. Summary

Security is not a feature—it’s a discipline. By applying OCI’s VCN, NSG, IAM, and logging tools correctly, you build a hardened cloud environment that minimizes attack surface and maximizes reliability.

👉 Download your free guide:
7 OCI Networking Mistakes to Avoid
https://dmcloudarchitect.com/c/7_oci_mistakes_to_avoid.html

Tags: #Best Practices

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