Creating a custom VPC in AWS - Practice Exercises

Challenge - 5 Problems

❓ Architecture

intermediate

VPC CIDR Block Size Calculation

You create a custom VPC with the CIDR block 10.0.0.0/20. How many IP addresses are available for use in this VPC?

A 4096 IP addresses

B 2048 IP addresses

C 8192 IP addresses

D 1024 IP addresses

💡 Hint

Remember that the number of IP addresses in a CIDR block is 2^(32 - prefix length).

A /20 CIDR block means 32 - 20 = 12 bits for hosts. 2^12 = 4096 IP addresses.

❓ Configuration

intermediate

Subnet Creation in a Custom VPC

You have a VPC with CIDR block 192.168.0.0/16. You want to create a subnet with CIDR 192.168.1.0/24. Which statement is true about this subnet?

A The subnet contains 256 IP addresses, but 5 are reserved by AWS.

B The subnet contains 128 IP addresses, all usable by instances.

C The subnet contains 512 IP addresses, but 5 are reserved by AWS.

D The subnet contains 256 IP addresses, all usable by instances.

💡 Hint

A /24 subnet has 256 IP addresses, but AWS reserves some IPs.

A /24 subnet has 256 IP addresses. AWS reserves 5 IP addresses in each subnet for network and AWS use.

❓ security

advanced

Security Group Behavior in a Custom VPC

You create a security group in your custom VPC that allows inbound SSH (port 22) from 0.0.0.0/0. What is the security implication of this configuration?

A Only IP addresses within the VPC can connect via SSH to instances using this security group.

B No IP addresses can connect via SSH because the rule is invalid.

C Only IP addresses explicitly whitelisted in the subnet can connect via SSH.

D Any IP address on the internet can attempt to connect via SSH to instances using this security group.

💡 Hint

Consider what 0.0.0.0/0 means in network rules.

The CIDR 0.0.0.0/0 means all IPv4 addresses. This allows any internet IP to attempt SSH connection.

❓ service_behavior

advanced

Internet Gateway Attachment Effect

You create a custom VPC and attach an Internet Gateway (IGW) to it. What effect does attaching the IGW have on the VPC?

A It blocks all inbound traffic from the internet to the VPC.

B It automatically assigns public IP addresses to all instances in the VPC.

C It enables instances in public subnets to communicate with the internet if route tables are configured correctly.

D It creates a VPN connection to AWS managed services.

💡 Hint

Think about what an Internet Gateway does in AWS networking.

An Internet Gateway allows communication between instances in public subnets and the internet, but route tables and public IPs must be configured properly.

✅ Best Practice

expert

Designing a Highly Available Custom VPC Architecture

You need to design a custom VPC architecture that supports high availability for a web application across two Availability Zones (AZs). Which design best meets this requirement?

A Create one public subnet in a single AZ and multiple private subnets in the other AZ, with a single NAT Gateway in the public subnet.

B Create one public subnet and one private subnet in each AZ, with a NAT Gateway in each public subnet for outbound internet access from private subnets.

C Create multiple public subnets in one AZ only, and private subnets in both AZs, sharing a single NAT Gateway in the public subnet.

D Create one public subnet and one private subnet in a single AZ only, with a NAT Gateway in the private subnet.

💡 Hint

Consider fault tolerance and redundancy across AZs.

For high availability, subnets and NAT Gateways should be in each AZ to avoid single points of failure.