Default VPC and subnets in GCP - Step-by-Step Execution

Process Flow - Default VPC and subnets

Create Default VPC

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Auto-create Subnets in each region

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Assign default firewall rules

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Ready for VM instances to use

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User can modify or add resources

The cloud automatically creates a default network with subnets in each region and sets firewall rules so you can start using it immediately.

Execution Sample

GCP

gcloud compute networks describe default
# Shows default VPC and its subnets

This command shows the default VPC and the subnets created automatically in each region.

Process Table

Step	Action	Result	Details
1	Create new GCP project	Project created	No VPC yet
2	Default VPC auto-created	VPC named 'default' exists	Network with auto mode
3	Subnets auto-created	One subnet per region	Each subnet has a CIDR block
4	Default firewall rules applied	Rules allow SSH, RDP, ICMP	Basic security rules set
5	User launches VM	VM attached to default subnet	VM gets internal IP from subnet
6	User modifies firewall	Rules updated	Can allow/block traffic
7	User adds custom subnet	New subnet created	User controls IP range
8	End	Default VPC ready for use	User can build on this network

💡 Default VPC and subnets are created automatically when a new project is made, ready for use.

Status Tracker

Resource	Initial State	After Step 2	After Step 3	After Step 7	Final
VPC Network	None	default VPC exists	default VPC with subnets	default VPC with subnets + custom subnet	default VPC with all subnets
Subnets	None	None	Subnets in all regions	Subnets + 1 custom subnet	All subnets active
Firewall Rules	None	Default rules applied	Default rules active	Default rules + user changes	Final firewall rules set

Key Moments - 3 Insights

Why do I see subnets in all regions even if I didn't create them?

Because the default VPC is in auto mode, it automatically creates one subnet in each region as shown in execution_table step 3.

Can I delete the default VPC or its subnets?

Yes, but you must first delete or move resources using them. The default VPC is just a starting point, as seen in step 7 where user adds custom subnets.

What firewall rules come with the default VPC?

Default firewall rules allow basic traffic like SSH, RDP, and ICMP, applied automatically at step 4 in the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, at which step are subnets created automatically in all regions?

A Step 2

B Step 5

C Step 3

D Step 7

💡 Hint

Check the 'Action' and 'Result' columns for subnet creation in execution_table row 3.

According to variable_tracker, what is the state of firewall rules after step 4?

A Default firewall rules applied

B No firewall rules

C User-defined firewall rules only

D Firewall rules deleted

💡 Hint

Look at the 'Firewall Rules' row and the 'After Step 2' and 'After Step 3' columns in variable_tracker.

If a user adds a custom subnet, which step in execution_table shows this change?

A Step 5

B Step 7

C Step 4

D Step 8

💡 Hint

Look for 'custom subnet' in the 'Action' column of execution_table.

Concept Snapshot

Default VPC is auto-created in new GCP projects.
It has one subnet per region by default.
Default firewall rules allow basic traffic.
Users can add or modify subnets and rules.
Ready to launch VM instances immediately.

Full Transcript

When you create a new Google Cloud project, a default virtual private cloud (VPC) network is automatically created. This default VPC is in auto mode, which means it automatically creates one subnet in each region with a predefined IP range. Along with the network and subnets, default firewall rules are applied to allow common traffic like SSH and ICMP. This setup lets you quickly launch virtual machines without manual network configuration. You can later add custom subnets or modify firewall rules as needed. The execution table shows each step from project creation to adding custom subnets, and the variable tracker shows how the network, subnets, and firewall rules change over time.