Networking Basics — 🌐 VPCs, Firewalls, and Connectivity

Cloud networking creates isolated, private networks for your applications. Understanding networking is critical for security and performance.

🎯 Virtual Private Cloud (VPC)

A VPC is your private network in the cloud. Think of it as renting a building and creating internal networks.

Your VPC (Private Network)
├── Subnet 1 (10.0.1.0/24)
│   └── Web servers (isolated)
├── Subnet 2 (10.0.2.0/24)
│   └── Database servers (isolated)
└── Router
    └── Internet Gateway (connects to internet)

Benefits:

• Isolation: Only your resources in your VPC

• Control: You define network structure

• Security: Restrict who can access what

• Privacy: Private IP addresses for internal communication

Cloud VPCs:

• AWS: VPC

• GCP: VPC Network

• Azure: Virtual Network

💡 Firewalls and Security Groups

Firewalls control which traffic is allowed in/out.

Inbound Rules: What can access your servers?

Outbound Rules: What can your servers access?

Example:

Inbound Rules:
- Allow HTTP (port 80) from anywhere
- Allow HTTPS (port 443) from anywhere
- Allow SSH (port 22) from office IP only

Outbound Rules:
- Allow all outbound traffic

Why this matters:

Without firewall rules, your database could be world-accessible (bad).

With rules, only your app servers can access database (good).

📊 Network Architecture Example

Internet (Public)
        ↓
    [Load Balancer]
        ↓
VPC (Private Network)
├── [Web Server 1]
├── [Web Server 2]
├── [Web Server 3]
└── [Database]

Traffic flow:

1. User requests come from internet

2. Load balancer routes to web servers

3. Web servers connect to database (private)

4. Database inaccessible from internet

5. Result: Secure, scalable architecture

💰 Connectivity Options

Internet-connected

Resources accessible from internet. Use for web servers, APIs.

Private (No Internet)

Resources only accessible within VPC. Use for databases, internal services.

Hybrid

Connect your on-premise network to cloud VPC.

Example: Company network ↔ VPN ↔ Cloud VPC

All systems work as if same network.

🎨 Real-World Example: E-commerce Architecture

Users on Internet
      ↓
Load Balancer (public, available to all)
      ↓
Web Servers (public subnet, can receive requests)
      ↓
App Servers (private subnet, internal only)
      ↓
Database (private subnet, internal only)

Security:

• Users can't directly access database

• Users can't directly access app servers

• Only web servers exposed to internet

• Database completely protected

🔑 Key Networking Concepts

✅ Networking Best Practices

1. Least Privilege: Only allow necessary traffic

2. Multi-tier: Separate web, app, database layers

3. Private Databases: Never expose databases to internet

4. Monitoring: Log and monitor network traffic

5. DDoS Protection: Use cloud provider's DDoS protection

🔑 Key Takeaways

• ✅ VPC is your isolated private network

• ✅ Security groups act as firewalls

• ✅ Subnet separates resources by function

• ✅ Databases should never be public

• ✅ Load balancers distribute traffic

• ✅ VPN secures remote connections

• ✅ Proper networking is critical for security

Want advanced patterns? 🌐 Networking Basics (Experienced)