Networking - C# Mastery Hub

What is VPC?

VPC (Virtual Private Cloud) is your private network in AWS. Think of it as your own personal data center in the cloud.

Isolated from other AWS customers

You control IP addresses, subnets, routing

Security with Security Groups and NACLs

Connect to the internet via Internet Gateway

Every AWS account gets a default VPC when you create it. You can use it or create your own.

VPC Components Explained

Component	Description	Analogy
VPC	Your private network	A house
Subnet	A section of your VPC	Rooms in the house
Internet Gateway	Connects VPC to internet	Front door
Route Table	Controls traffic routing	House map
Security Group	Firewall for instances	Room locks
NACL	Firewall for subnets	House security system

Subnets - Dividing Your VPC

A Subnet is a range of IP addresses in your VPC. You divide your VPC into subnets to organize resources.

Public Subnet

Has internet access via Internet Gateway. Used for web servers, load balancers.

Private Subnet

No direct internet access. Used for databases, application servers.

Best Practice: Always use at least 2 subnets in different Availability Zones for high availability.

Security Groups - Your First Line of Defense

A Security Group acts as a virtual firewall for your EC2 instances. It controls inbound and outbound traffic.

Inbound Rules

Controls what traffic can enter your instance.

Example: Allow SSH (port 22) from your IP

Outbound Rules

Controls what traffic can leave your instance.

Example: Allow all outbound traffic

Remember: Security Groups are stateful - if you allow inbound, outbound is automatically allowed.

Exercise: Create a VPC

Task: Create a VPC with public and private subnets.

Create a VPC with CIDR block 10.0.0.0/16
Create 2 public subnets (10.0.1.0/24, 10.0.2.0/24)
Create 2 private subnets (10.0.3.0/24, 10.0.4.0/24)
Create an Internet Gateway and attach it
Create a route table and associate with public subnets
Launch an EC2 instance in a public subnet
Connect to it and verify internet access

Show Solution

# 1. Create VPC
aws ec2 create-vpc --cidr-block 10.0.0.0/16

# 2. Create Subnets
aws ec2 create-subnet --vpc-id vpc-xxx --cidr-block 10.0.1.0/24 --availability-zone us-east-1a
aws ec2 create-subnet --vpc-id vpc-xxx --cidr-block 10.0.2.0/24 --availability-zone us-east-1b
aws ec2 create-subnet --vpc-id vpc-xxx --cidr-block 10.0.3.0/24 --availability-zone us-east-1a
aws ec2 create-subnet --vpc-id vpc-xxx --cidr-block 10.0.4.0/24 --availability-zone us-east-1b

# 3. Create and attach Internet Gateway
aws ec2 create-internet-gateway
aws ec2 attach-internet-gateway --internet-gateway-id igw-xxx --vpc-id vpc-xxx

# 4. Create route table for public subnets
aws ec2 create-route-table --vpc-id vpc-xxx
aws ec2 create-route --route-table-id rtb-xxx --destination-cidr-block 0.0.0.0/0 --gateway-id igw-xxx
aws ec2 associate-route-table --route-table-id rtb-xxx --subnet-id subnet-xxx

Key Takeaway

VPC is your private network in AWS. Use public subnets for resources that need internet access and private subnets for internal resources. Security Groups are your first line of defense for EC2 instances.

AWS Networking