Custom VPC creation in GCP - Step-by-Step Execution

Process Flow - Custom VPC creation

Start

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Define VPC Name & Region

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Specify Subnet Ranges

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Create VPC Network

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Create Subnets in VPC

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Set Firewall Rules (optional)

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VPC Ready for Use

This flow shows the steps to create a custom VPC: define name and region, specify subnet IP ranges, create the VPC network, add subnets, optionally set firewall rules, then the VPC is ready.

Execution Sample

GCP

gcloud compute networks create my-custom-vpc --subnet-mode=custom

gcloud compute networks subnets create my-subnet-1 --network=my-custom-vpc --region=us-central1 --range=10.0.1.0/24

gcloud compute firewall-rules create allow-internal --network=my-custom-vpc --allow tcp,udp,icmp --source-ranges=10.0.0.0/16

This code creates a custom VPC, adds a subnet with a specific IP range, and sets a firewall rule to allow internal traffic.

Process Table

Step	Action	Command	Result
1	Create custom VPC network	gcloud compute networks create my-custom-vpc --subnet-mode=custom	VPC 'my-custom-vpc' created with no subnets
2	Create subnet in VPC	gcloud compute networks subnets create my-subnet-1 --network=my-custom-vpc --region=us-central1 --range=10.0.1.0/24	Subnet 'my-subnet-1' created in 'us-central1' with IP range 10.0.1.0/24
3	Create firewall rule to allow internal traffic	gcloud compute firewall-rules create allow-internal --network=my-custom-vpc --allow tcp,udp,icmp --source-ranges=10.0.0.0/16	Firewall rule 'allow-internal' created allowing tcp, udp, icmp from 10.0.0.0/16
4	Verify VPC and subnet	gcloud compute networks describe my-custom-vpc	Shows VPC with custom subnet 'my-subnet-1' and firewall rules
5	End	-	Custom VPC setup complete and ready for use

💡 All steps completed successfully; custom VPC with subnet and firewall rule is ready.

Status Tracker

Resource	Initial State	After Step 1	After Step 2	After Step 3	Final State
VPC Network	None	Created (no subnets)	Created (no change)	Created (no change)	Exists with subnet and firewall rules
Subnet	None	None	Created with 10.0.1.0/24 in us-central1	Created (no change)	Exists in VPC
Firewall Rules	None	None	None	Created allowing internal traffic	Exists and active

Key Moments - 2 Insights

Why do we specify --subnet-mode=custom when creating the VPC?

Because by default, VPCs create automatic subnets in all regions. Using --subnet-mode=custom means no subnets are created automatically, so you can add subnets with your own IP ranges as shown in step 2.

What happens if we skip creating firewall rules after creating the VPC and subnet?

By default, the VPC blocks most traffic. Without firewall rules like in step 3, instances in the subnet cannot communicate internally or externally as desired.

Visual Quiz - 3 Questions

Look at the execution table, what is the IP range of the subnet created at step 2?

A 10.0.1.0/24

B 10.0.0.0/16

C 192.168.1.0/24

D 172.16.0.0/16

💡 Hint

Check the 'Command' and 'Result' columns in row 2 of the execution table.

At which step is the firewall rule created to allow internal traffic?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the action mentioning firewall rules in the execution table.

If we omit --subnet-mode=custom in step 1, what changes in the execution?

A No subnets are created at all

B Subnets are created automatically in all regions

C Firewall rules are created automatically

D The VPC creation fails

💡 Hint

Refer to the key moment about subnet mode and step 1 in the execution table.

Concept Snapshot

Custom VPC creation in GCP:
- Use 'gcloud compute networks create NAME --subnet-mode=custom' to create empty VPC
- Add subnets with 'gcloud compute networks subnets create' specifying region and IP range
- Set firewall rules to allow traffic as needed
- Custom VPC gives control over subnet IP ranges and network policies

Full Transcript

To create a custom VPC in Google Cloud, first run the command to create a VPC network with subnet mode set to custom. This prevents automatic subnet creation. Next, create subnets inside this VPC by specifying the region and IP address range. Then, add firewall rules to allow internal traffic between instances. The execution table shows each step with commands and results. Variables track the state of the VPC, subnets, and firewall rules as they are created. Key moments clarify why subnet mode custom is important and the role of firewall rules. The visual quiz tests understanding of subnet IP ranges, firewall creation step, and subnet mode effects. The snapshot summarizes the commands and purpose of each step.