GCP Networking Basics: VPCs, Subnets, and Routes Explained

Tutorial RSH Network December 16, 2025 2 mins read

This guide breaks down GCP networking fundamentals—VPCs, subnets, and routes—to help you architect secure and scalable cloud networks.

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1. Introduction

Networking is the backbone of cloud infrastructure. In Google Cloud Platform (GCP), Virtual Private Cloud (VPC) provides a scalable and secure networking foundation for all your cloud resources. Understanding how VPCs, subnets, and routes work together is essential for designing reliable, high-performance cloud architectures.

2. What Is a VPC in GCP?

A VPC is a logically isolated, private network within GCP.

Key Characteristics

  • Global by design (spans multiple regions)

  • Defines IP ranges, subnets, firewall rules, and routes

  • Supports hybrid connectivity (VPN, Interconnect)

  • Default VPC is auto-created with preconfigured rules (not recommended for production)

3. Subnets in GCP

Subnets are regional IP address ranges within a VPC.

Subnet Features

  • Defined using CIDR blocks (e.g., 10.0.0.0/24)

  • VMs receive internal IPs from subnet ranges

  • Can span multiple availability zones within a region

  • Supports:

    • Auto mode (GCP creates subnets automatically)

    • Custom mode (you define subnet IP ranges manually)

➡️ Best Practice: Use custom mode for production environments.

4. Routes in GCP

Routes control how network traffic flows within a VPC and to external destinations.

Each Route Includes

  • Destination IP range

  • Next hop (internet gateway, VPN, peering)

  • Priority (lower number = higher priority)

Common Routes

  • Default route: 0.0.0.0/0 → Internet Gateway

  • Subnet routes: auto-created for internal traffic

  • Custom routes: for hybrid or advanced routing scenarios

5. Creating a Custom VPC (GCP Console)

Step-by-Step

  1. Navigate to VPC Network → VPC Networks

  2. Click Create VPC Network

  3. Enter a VPC name

  4. Select Custom Mode

  5. Add subnets with:

    • Region

    • IP CIDR range

  6. Review and click Create

6. CLI Example (gcloud)

 
# Create a custom VPC gcloud compute networks create my-vpc --subnet-mode=custom # Create a subnet gcloud compute networks subnets create my-subnet \ --network=my-vpc \ --region=us-central1 \ --range=10.0.1.0/24

7. Best Practices

✅ Use custom VPCs for production
✅ Segment workloads using regional subnets
✅ Apply firewall rules to restrict access
✅ Enable VPC Flow Logs for visibility
✅ Avoid overlapping IP ranges across projects
✅ Separate dev, test, and prod networks

8. Visual Guide (Image Suggestions)

  • Diagram: VPC → Subnets → Routes → Firewall

  • Screenshot: VPC creation screen in GCP Console

  • Infographic: Labeled VPC architecture flow

9. Conclusion

Mastering GCP networking fundamentals enables you to build secure, scalable, and highly available cloud environments. By understanding VPCs, subnets, and routes, you gain full control over traffic flow and network isolation.

📘 Next Post: Setting Up Load Balancers in GCP for High Availability

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