Default VPC overview in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main purpose of a Default VPC in AWS?

Imagine you just created a new AWS account. AWS automatically creates a Default VPC for you. What is the main purpose of this Default VPC?

A It automatically creates private subnets only, so instances cannot access the internet.

B It restricts all network traffic by default to increase security.

C It provides a ready-to-use network environment so you can launch instances without configuring networking.

D It is a backup network that activates only if you delete your custom VPCs.

💡 Hint

Think about what happens when you launch an instance without creating any network settings.

The Default VPC is designed to let users launch instances immediately with internet access and basic networking without extra setup.

❓ Architecture

intermediate

Which components are included by default in an AWS Default VPC?

When AWS creates a Default VPC in your account, which of the following components does it include by default?

A Only private subnets with no internet gateway attached.

B No subnets, only a virtual private gateway.

C Multiple NAT gateways and no internet gateway.

D One public subnet in each Availability Zone, an internet gateway, and default route tables.

💡 Hint

Think about how instances in the Default VPC can access the internet.

The Default VPC includes one public subnet per AZ, an internet gateway attached, and route tables that send internet traffic through the gateway.

❓ security

advanced

What is the default security group behavior in a Default VPC?

Consider the default security group created with the Default VPC. What is its default behavior regarding inbound and outbound traffic?

A Allows all outbound traffic and inbound traffic only from instances assigned to the same security group.

B Allows all inbound and outbound traffic from any source.

C Blocks all inbound and outbound traffic by default.

D Allows inbound traffic from the internet but blocks all outbound traffic.

💡 Hint

Think about how instances in the same security group communicate by default.

The default security group allows all outbound traffic and inbound traffic only from instances assigned to the same group, providing basic isolation.

❓ service_behavior

advanced

What happens if you delete the Default VPC in your AWS account?

After deleting the Default VPC, what is the behavior of AWS regarding Default VPCs in your account?

A AWS does not recreate it automatically; you must create a new VPC manually.

B AWS automatically recreates the Default VPC after 24 hours.

C AWS creates a Default VPC only when you launch your first instance after deletion.

D AWS disables your account until you create a new Default VPC.

💡 Hint

Think about whether AWS automatically restores deleted resources.

Once deleted, the Default VPC is not recreated automatically. You must create your own VPC or use the VPC wizard.

✅ Best Practice

expert

Which is the best practice regarding the use of Default VPCs in production environments?

For a secure and scalable production environment, what is the recommended approach to using Default VPCs?

A Use the Default VPC as is, since it is preconfigured for internet access and easy setup.

B Delete the Default VPC and create custom VPCs with tailored subnetting, routing, and security controls.

C Use multiple Default VPCs across regions to increase redundancy.

D Keep the Default VPC but disable the internet gateway to prevent internet access.

💡 Hint

Think about control and security needs in production.

Production environments benefit from custom VPCs designed for specific security, subnet, and routing needs rather than relying on the Default VPC.

Practice

1. What is the main purpose of the AWS Default VPC?

easy

A. To monitor application performance

B. To store data backups automatically

C. To provide a ready-to-use network for launching resources quickly

D. To manage user permissions and roles

Solution

1. Step 1: Understand what a VPC is

   A VPC is a virtual network where AWS resources run.

2. Step 2: Identify the role of the Default VPC

   The Default VPC is pre-made to let users launch resources without extra setup.

3. Final Answer:

   To provide a ready-to-use network for launching resources quickly -> Option C

4. Quick Check:

   Default VPC = ready network [OK]

Hint: Default VPC means ready network for quick resource launch [OK]

Common Mistakes:

• Confusing VPC with storage or permissions
• Thinking Default VPC manages backups
• Assuming Default VPC monitors performance

2. Which of the following is TRUE about the Default VPC's subnets?

easy

A. Subnets must be created manually before use

B. It has no subnets by default

C. It only has private subnets without internet access

D. It includes one subnet in each Availability Zone

Solution

1. Step 1: Recall Default VPC subnet setup

   The Default VPC automatically creates one subnet per Availability Zone.

2. Step 2: Check internet access for subnets

   These subnets are public and have internet access by default.

3. Final Answer:

   It includes one subnet in each Availability Zone -> Option D

4. Quick Check:

   Default VPC = subnet per AZ [OK]

Hint: Default VPC auto-creates subnets per AZ [OK]

Common Mistakes:

• Thinking Default VPC has no subnets
• Assuming subnets are private only
• Believing subnets require manual creation

3. If you launch an EC2 instance in the Default VPC, what is the default behavior regarding internet access?

medium

A. The instance automatically gets a public IP and internet access

B. The instance can only access other instances in the same subnet

C. The instance has no internet access unless manually configured

D. The instance is blocked from all network traffic by default

Solution

1. Step 1: Understand Default VPC internet setup

   Default VPC subnets are public and assign public IPs automatically.

2. Step 2: Check instance network behavior

   Instances launched get internet access by default through the internet gateway.

3. Final Answer:

   The instance automatically gets a public IP and internet access -> Option A

4. Quick Check:

   Default VPC instance = public IP + internet [OK]

Hint: Default VPC instances get public IPs automatically [OK]

Common Mistakes:

• Assuming no internet without manual setup
• Thinking instances are isolated by default
• Believing network traffic is blocked initially

4. You try to launch an EC2 instance in the Default VPC but get a network error. What is the most likely cause?

medium

A. The Default VPC was deleted or modified incorrectly

B. You forgot to create a subnet manually

C. The instance type is not supported in the Default VPC

D. AWS does not allow EC2 in Default VPC

Solution

1. Step 1: Recall Default VPC properties

   Default VPC exists by default with subnets and internet gateway.

2. Step 2: Analyze network error cause

   If network errors occur, it often means the Default VPC was deleted or changed wrongly.

3. Final Answer:

   The Default VPC was deleted or modified incorrectly -> Option A

4. Quick Check:

   Network error = Default VPC missing/changed [OK]

Hint: Network errors often mean Default VPC missing or changed [OK]

Common Mistakes:

• Assuming subnets must be created manually
• Thinking instance type blocks launch
• Believing EC2 is disallowed in Default VPC

5. You want to launch a private EC2 instance without internet access using the Default VPC. What should you do?

hard

A. Launch in the Default VPC subnet and disable the public IP

B. Create a new private subnet in the Default VPC and launch the instance there

C. Use the Default VPC as is; all instances are private by default

D. Delete the Default VPC and create a custom VPC with no internet gateway

Solution

1. Step 1: Understand Default VPC subnet types

   Default VPC subnets are public with internet access by default.

2. Step 2: Plan for private instance launch

   To have a private instance, create a new private subnet without internet gateway attachment.

3. Step 3: Avoid deleting Default VPC unnecessarily

   Deleting Default VPC is not required; just add private subnet inside it.

4. Final Answer:

   Create a new private subnet in the Default VPC and launch the instance there -> Option B

5. Quick Check:

   Private instance = new private subnet in Default VPC [OK]

Hint: Add private subnet in Default VPC for no internet [OK]

Common Mistakes:

• Assuming disabling public IP alone makes instance private
• Thinking all Default VPC instances are private
• Deleting Default VPC unnecessarily