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Introduction
If you're new to Google Cloud Platform (GCP), one of the first hurdles you'll face is understanding how everything connects. How do virtual machines talk to each other? How do you expose an app to the internet securely? Why do some services fail to communicate, even when you've followed the instructions?
Welcome to GCP networking — the part that feels invisible until something breaks.
But don’t worry. This guide is designed to make GCP networking not just understandable, but practical and hands-on. We’ll skip the jargon and walk you through the real-world components like VPCs, subnets, firewall rules, and routing in a way that makes sense. You'll not only learn the concepts but also practice them step-by-step, so you can build the confidence to troubleshoot and deploy cloud networks effectively.
Whether you’re a student, a career switcher, or preparing for a GCP certification, you’re in the right place. Let’s get started and take the mystery out of GCP networking.
Why GCP Networking Matters
GCP networking is foundational to nearly everything you do in the cloud:
Setting up secure communication between services
Exposing applications to the internet
Enforcing network segmentation for security
Managing traffic costs and latency
Without a strong understanding of networking, you're likely to face issues like failed VM connections, open attack surfaces, or unexpected egress charges.
Core Concepts of GCP Networking
What is a VPC (Virtual Private Cloud)?
A Virtual Private Cloud (VPC) in GCP is a logically isolated, customizable network. Think of it as your private data center in the cloud.
Key points:
A project can have multiple VPCs
VPCs span regions (they are global)
Subnets are regional
Subnets – Regional Divisions of a VPC
Each VPC is divided into one or more subnets, each within a specific region. Subnets are responsible for allocating IP ranges to VMs.
# Example: Create a subnet in custom VPC gcloud compute networks subnets create my-subnet \ --network=my-custom-vpc \ --region=us-central1 \ --range=10.0.1.0/24
Firewalls in GCP
GCP automatically blocks all incoming traffic unless explicitly allowed. Firewalls in GCP are stateful, meaning return traffic is allowed automatically.
Default Rules:
Allow internal (10.128.0.0/9) communication
Allow SSH (port 22) from anywhere (can be removed)
Deny all incoming by default
Routes and Routing Tables
Every VPC has a default route to the internet via the default internet gateway. Routes determine where traffic should go based on IP addresses.
# View routes gcloud compute routes list --filter="network=my-custom-vpc"
External and Internal IPs
Internal IP: Used for communication within the VPC.
External IP: Publicly accessible IP. Needed to reach the internet.
Tip: Assign static external IPs for servers that need consistent public access.
Hands-on Example: Creating a Custom VPC with Two Subnets
Step 1: Open Google Cloud Console
Navigate to https://console.cloud.google.com and select your project.
Step 2: Create a Custom VPC Network
Go to VPC Network > VPC Networks > Create VPC Network
Name it my-custom-vpc
Choose Custom subnet creation mode
Step 3: Add Two Regional Subnets
Add subnet subnet-a in region us-central1 with IP range 10.0.1.0/24
Add subnet subnet-b in region us-east1 with IP range 10.0.2.0/24
# CLI Equivalent gcloud compute networks create my-custom-vpc --subnet-mode=custom gcloud compute networks subnets create subnet-a --network=my-custom-vpc --region=us-central1 --range=10.0.1.0/24 gcloud compute networks subnets create subnet-b --network=my-custom-vpc --region=us-east1 --range=10.0.2.0/24
Step 4: Add Firewall Rules
Create a rule to allow SSH, ICMP (ping), and internal communication.
# Allow SSH and ICMP gcloud compute firewall-rules create allow-ssh-icmp \ --network=my-custom-vpc \ --allow=tcp:22,icmp \ --source-ranges=0.0.0.0/0
Step 5: Test Communication Between VM Instances
Create one VM in each subnet, then SSH into them to ping each other.
How This Helps with GCP Certification
This guide aligns with Associate Cloud Engineer and Cloud Architect certifications. Topics covered include:
VPC design and subnetting
Configuring firewall rules
Managing routes
Hands-on GCP Console and CLI usage
Expect questions like:
"How do you isolate workloads in GCP?" "How do you allow SSH access from a specific IP?"
Explore More with Certkraft Labs
At Certkraft, we believe that you learn best by doing.
Our GCP Networking Labs include:
Interactive VPC creation walkthroughs
Quizzes embedded in labs
Real-world traffic simulation scenarios