Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A company is deploying a three-tier web application on AWS. The security team requires a network-level firewall that operates at the subnet level and can evaluate both inbound and outbound traffic using stateless rules. Which AWS feature should the company use to meet this requirement?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Security Groups
Security Groups are stateful and operate at the instance level (elastic network interface), not at the subnet level. They cannot be used to control traffic for an entire subnet with a single rule set.
B
Best answer
Network ACLs
Network ACLs are a stateless firewall operating at the subnet level, supporting both inbound and outbound rules. They evaluate traffic based on rule order and allow or deny traffic without maintaining connection state, matching the requirement.
C
Distractor review
AWS WAF
AWS WAF is a web application firewall that works at Layer 7 to protect against common web exploits. It does not provide subnet-level network firewall capabilities and is not designed for general network traffic control.
D
Distractor review
AWS Shield
AWS Shield is a managed DDoS protection service that safeguards applications against distributed denial-of-service attacks. It does not function as a subnet-level firewall with inbound/outbound rule evaluation.
Common exam trap
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Technical deep dive
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A developer needs to launch a test server for a new application prototype. The developer logs into the AWS Management Console, selects an Amazon EC2 instance type, configures the security group, and starts the instance. The instance is running within two minutes, and the developer did not need to submit a formal request to the company's IT procurement team or wait for approval from a cloud administrator. Which essential characteristic of cloud computing does this scenario best demonstrate?
Question 2
A solutions architect is planning a new web application on AWS. The workload will include 3 Amazon EC2 instances (t3.medium) running 24/7, an Application Load Balancer, and an Amazon RDS for MySQL db.t3.small database. The architect needs to estimate the monthly cost for the first year, considering different purchasing options (On-Demand, 1-year All Upfront Reserved Instance, and Compute Savings Plan). Which AWS tool should the architect use to create this estimate?
Question 3
A company's development team frequently needs temporary test environments. A developer can log into the AWS Management Console, select an Amazon EC2 instance type, configure storage, and launch the instance within minutes without any interaction with the IT infrastructure team. This capability is an example of which essential characteristic of cloud computing?
Question 4
A company's finance team needs to analyze AWS spending in detail. They require a report that includes hourly cost data for each AWS service, each individual resource (e.g., a specific EC2 instance), and any cost allocation tags applied. The team plans to export this data to an Amazon S3 bucket and then import it into a custom business intelligence (BI) analytics dashboard. Which AWS tool should the finance team use to generate this level of detailed cost data?
Question 5
A company uses AWS for its development environment. The finance team wants to set a monthly budget of $10,000. They want to receive an email notification when the actual costs reach 80% of the budget ($8,000) and again when costs exceed the budget. The team needs a managed AWS service that can automatically send these alerts without requiring custom code or third-party tools. Which AWS service should the team use?
Question 6
A company uses AWS Organizations to manage multiple accounts. The security team needs to enforce a policy that restricts SSH access (port 22) from the internet (0.0.0.0/0) in all VPCs across all accounts. The team wants to centrally define the allowed rules and automatically apply them to newly created VPCs and security groups, while also automatically remediating any existing non-compliant security groups. Which AWS service should the team use?
FAQ
Questions learners often ask
What does this CLF-C02 question test?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: Network ACLs — The requirement specifies a network-level firewall at the subnet level with stateless rules. Network ACLs (Access Control Lists) are a security layer for your VPC that act as a firewall for controlling traffic in and out of one or more subnets. They are stateless, meaning they evaluate each packet independently without considering connection state. Security Groups are stateful and operate at the instance level, not subnet level. AWS WAF is a web application firewall that operates at Layer 7 (HTTP/HTTPS) to protect web applications. AWS Shield is a managed DDoS protection service and does not provide subnet-level firewall rules. Therefore, the correct choice is Network ACLs.
What should I do if I get this CLF-C02 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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