Creating a custom VPC in AWS - Visual Walkthrough

Process Flow - Creating a custom VPC

Start

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Define VPC CIDR

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Create VPC

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Create Subnets

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Create Internet Gateway

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Attach Internet Gateway to VPC

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Create Route Table

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Add Route to Internet Gateway

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Associate Route Table with Subnets

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End: Custom VPC Ready

The flow shows the steps to create a custom VPC: define IP range, create VPC, add subnets, set up internet gateway, route table, and associate them.

Execution Sample

AWS

aws ec2 create-vpc --cidr-block 10.0.0.0/16
aws ec2 create-subnet --vpc-id vpc-1234 --cidr-block 10.0.1.0/24
aws ec2 create-internet-gateway
aws ec2 attach-internet-gateway --vpc-id vpc-1234 --internet-gateway-id igw-1234
aws ec2 create-route-table --vpc-id vpc-1234
aws ec2 create-route --route-table-id rtb-1234 --destination-cidr-block 0.0.0.0/0 --gateway-id igw-1234
aws ec2 associate-route-table --subnet-id subnet-1234 --route-table-id rtb-1234

This sequence creates a VPC with a subnet, internet gateway, route table, and connects them for internet access.

Process Table

Step	Action	Resource Created/Modified	ID/Value	State After Action
1	Create VPC with CIDR 10.0.0.0/16	VPC	vpc-1234	VPC vpc-1234 created with CIDR 10.0.0.0/16
2	Create Subnet in VPC vpc-1234 with CIDR 10.0.1.0/24	Subnet	subnet-1234	Subnet subnet-1234 created in vpc-1234
3	Create Internet Gateway	Internet Gateway	igw-1234	Internet Gateway igw-1234 created
4	Attach Internet Gateway igw-1234 to VPC vpc-1234	Attachment	igw-1234 attached	Internet Gateway attached to VPC
5	Create Route Table in VPC vpc-1234	Route Table	rtb-1234	Route Table rtb-1234 created
6	Create Route 0.0.0.0/0 via igw-1234 in rtb-1234	Route	route-1	Route to internet added in route table
7	Associate Route Table rtb-1234 with Subnet subnet-1234	Association	assoc-1	Subnet uses route table with internet access
8	End	N/A	N/A	Custom VPC setup complete with internet access

💡 All resources created and connected; VPC is ready for use with internet access.

Status Tracker

Resource	Initial	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7	Final
VPC	None	vpc-1234 (CIDR 10.0.0.0/16)	vpc-1234	vpc-1234	vpc-1234	vpc-1234	vpc-1234	vpc-1234	vpc-1234
Subnet	None	None	subnet-1234 (CIDR 10.0.1.0/24)	subnet-1234	subnet-1234	subnet-1234	subnet-1234	subnet-1234 (associated)	subnet-1234 (associated)
Internet Gateway	None	None	None	igw-1234	igw-1234 attached	igw-1234 attached	igw-1234 attached	igw-1234 attached	igw-1234 attached
Route Table	None	None	None	None	rtb-1234	rtb-1234 with route	rtb-1234 with route	rtb-1234 with route	rtb-1234 with route

Key Moments - 3 Insights

Why do we need to attach the Internet Gateway to the VPC after creating it?

Creating the Internet Gateway alone does not connect it to the VPC. Step 4 attaches it, enabling internet traffic routing as shown in execution_table row 4.

What happens if we don't associate the route table with the subnet?

Without association (step 7), the subnet won't use the route table with internet access, so instances can't reach the internet. See execution_table row 7 for association importance.

Why define CIDR blocks when creating VPC and subnet?

CIDR blocks define IP address ranges. The VPC CIDR (step 1) is large, and subnet CIDR (step 2) is a smaller part inside it, ensuring organized IP allocation.

Visual Quiz - 3 Questions

Look at the execution_table at step 3. What resource is created?

A Route Table rtb-1234

B Subnet subnet-1234

C Internet Gateway igw-1234

D VPC vpc-1234

💡 Hint

Check the 'Resource Created/Modified' column at step 3 in execution_table.

At which step does the subnet get associated with the route table?

A Step 7

B Step 6

C Step 5

D Step 4

💡 Hint

Look for 'Associate Route Table' action in execution_table rows.

If the Internet Gateway was not attached to the VPC, what would be the state of internet access?

A Internet access would work normally

B Internet access would fail because IGW is not attached

C Subnet would have internet access without IGW

D Route table would automatically fix it

💡 Hint

Refer to key_moments explanation about attaching IGW and execution_table step 4.

Concept Snapshot

Creating a custom VPC:
- Define a CIDR block (IP range) for the VPC
- Create the VPC resource
- Create subnets inside the VPC with smaller CIDRs
- Create and attach an Internet Gateway for internet access
- Create a route table and add a route to the IGW
- Associate the route table with subnets
- Result: VPC with internet connectivity ready for instances

Full Transcript

To create a custom VPC, start by defining the IP address range using a CIDR block. Then create the VPC resource with this CIDR. Next, create one or more subnets inside the VPC, each with a smaller CIDR block. Create an Internet Gateway and attach it to the VPC to enable internet access. Create a route table for the VPC and add a route that sends all internet traffic (0.0.0.0/0) to the Internet Gateway. Finally, associate this route table with the subnets so that instances inside can use it. This setup allows instances in the subnet to communicate with the internet through the VPC.