☁️ VPC Network

 

☁️ VPC Network — Simple Notes

1. What is a VPC?

VPC (Virtual Private Cloud) is a virtual version of a physical network inside Google Cloud.

Think of it like your company's private network in the cloud.

It provides connectivity for:

  • Compute Engine VM instances
  • Google Kubernetes Engine (GKE) clusters
  • App Engine Flexible
  • Other Google Cloud services that use Compute Engine VMs

Simple example:

                Google Cloud
                     │
                ┌────▼────┐
                │   VPC   │
                └────┬────┘
          ┌──────────┼──────────┐
          ▼          ▼          ▼
         VM         VM         GKE

2. VPC and Load Balancing

VPC supports Google's internal networking and load-balancing systems.

It can provide:

  • Internal pass-through Network Load Balancers
  • Internal proxy-based Application Load Balancers
  • Connectivity for external load balancers to their backend services

Think:

Users
  │
  ▼
External Load Balancer
  │
  ▼
VPC Network
  │
  ├── VM 1
  ├── VM 2
  └── VM 3

3. Connecting VPC to On-Premises Network

Your company may have servers in its own data center (on-premises).

VPC can connect Google Cloud to that network using:

  • Cloud VPN → encrypted connection over the internet
  • Cloud Interconnect → dedicated/private connection

Simple picture:

Company Data Center
       │
       │
  VPN / Interconnect
       │
       ▼
 Google Cloud VPC
       │
       ▼
      VMs

🛣️ 4. Routes in a VPC

A route tells Google Cloud:

"Where should this packet go?"

Every VPC automatically has routes that allow VMs to communicate with each other, even when the VMs are in different subnets.

Example:

Subnet A
10.1.0.0/24
     │
     │ route
     ▼
Subnet B
10.2.0.0/24

A VM in 10.1.0.0/24 can route traffic to a VM in 10.2.0.0/24.

Default Internet Route

A VPC also has a default route that sends traffic destined outside the VPC toward the internet gateway.

Conceptually:

VM
 │
 ▼
VPC Route
 │
 ├── Internal destination → another VM/subnet
 │
 └── External destination → Internet

⭐ 5. Custom Routes

The default routes handle most normal requirements.

But you can create custom/special routes when you need different traffic behavior.

For example:

VM
 │
 ▼
Custom Route
 │
 ▼
Specific Next Hop

Important ⚠️

Creating a route does NOT automatically mean the traffic will be accepted.

You also need an appropriate firewall rule.

Remember:

Route = Where should the packet go?
Firewall = Is the packet allowed?

Both may be required.

🔥 6. Firewall Rules

Firewall rules control whether network traffic is allowed or denied.

Default VPC Network

The default network comes with preconfigured firewall rules that allow instances in the network to communicate with each other.

Custom VPC Network

If you manually create a custom-mode VPC, those default firewall rules are not automatically created.

So you need to create the required firewall rules yourself.

This is one reason custom VPCs require more planning.

🏢 7. Multiple VPC Networks in One Project

A single Google Cloud project can contain multiple VPC networks.

Example:

Project
│
├── production-vpc
│
├── development-vpc
│
└── testing-vpc

Each VPC can have its own subnets, routes and firewall configuration.

🌎 8. Default Network and Auto Mode

Normally, when a new Google Cloud project is created, it starts with a default VPC network in auto mode, unless an organization policy prevents this.

Auto Mode VPC

An auto-mode VPC automatically creates one subnet in each Google Cloud region.

For example:

Auto Mode VPC
│
├── us-east4 subnet
├── asia-east1 subnet
├── europe-west1 subnet
├── ...
└── other regions

This is convenient when you're learning Google Cloud because you don't need to manually create every subnet.

⭐ 9. Auto Mode vs Custom Mode

FeatureAuto ModeCustom Mode
SubnetsAutomatically createdYou create them
One subnet per regionYesNo
ControlLessMore
Good for learning✅ Yes✅
Production planningUsually less suitable✅ Common choice

Best Practice

Google recommends using custom-mode VPC networks when you need control over which regions contain subnets.

Instead of automatically getting:

Subnet in every region

you can choose only what you need:

My Custom VPC
│
├── asia-south1 subnet
└── us-east4 subnet

This gives you better control over your network design.

🧠 Remember These 7 Points

  1. VPC = Virtual network in Google Cloud.
  2. VPC provides connectivity for VMs, GKE, App Engine Flexible, etc.
  3. Routes decide where traffic goes.
  4. Firewall rules decide whether traffic is allowed.
  5. A route alone doesn't guarantee successful communication.
  6. Auto mode automatically creates a subnet in every region.
  7. Custom mode lets you choose exactly which regions/subnets you need and is generally the preferred approach for planned environments.

🔑 One-line memory trick

VPC = Network, Subnet = IP range, Route = Path, Firewall = Permission.

Comments

Post a Comment

Popular posts from this blog

Async/await

  Async/await An async function is a function declared with the async keyword, and the await keyword is permitted within them. The async and await keywords enable asynchronous, promise-based behavior to be written in a cleaner style, avoiding the need to explicitly configure promise chains. "async and await make promises easier to write" async  makes a function return a Promise await  makes a function wait for a Promise  Async functions Let’s start with the async keyword. It can be placed before a function, like this: async function f() {   return 1; } The word “async” before a function means one simple thing: a function always returns a promise. Other values are wrapped in a resolved promise automatically. For instance, this function returns a resolved promise with the result of 1; let’s test it: async function f() {   return 1; } f().then(alert); // 1 …We could explicitly return a promise, which would be the same: async function f() {   return Promis...
Read more

First negative in every window of size k

 Given an array arr[]  and a positive integer k, find the first negative integer for each and every window(contiguous subarray) of size k. Note: If a window does not contain a negative integer, then return 0 for that window. Examples: Input: arr[] = [-8, 2, 3, -6, 10] , k = 2 Output: [-8, 0, -6, -6] Explanation: Window [-8, 2] First negative integer is -8. Window [2, 3] No negative integers, output is 0. Window [3, -6] First negative integer is -6. Window [-6, 10] First negative integer is -6. Input: arr[] = [12, -1, -7, 8, -15, 30, 16, 28] , k = 3 Output: [-1, -1, -7, -15, -15, 0]  Explanation: Window [12, -1, -7] First negative integer is -1. Window [-1, -7, 8] First negative integer is -1. Window [-7, 8, -15] First negative integer is -7. Window [8, -15, 30] First negative integer is -15. Window [-15, 30, 16] First negative integer is -15. Window [30, 16, 28] No negative integers, output is 0. Input: arr[] = [12, 1, 3, 5] , k = 3 Output: [0, 0]  Explanation: Windo...
Read more

Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type.   Example 1: Input: s = "()" Output: true Example 2: Input: s = "()[]{}" Output: true Example 3: Input: s = "(]" Output: false Example 4: Input: s = "([])" Output: true   Stack-Based Logic: Traverse each character in the string. If it's an opening bracket ( '(' , '{' , '[' ), push it onto the stack. If it's a closing bracket ( ')' , '}' , ']' ): If the stack is empty , return false (nothing to match). If the top of the stack is the corresponding opening bracket , pop it. Otherwise, return false . ...
Read more