- A
ARP scan with arp-scan
ARP operates at Layer 2 and is not blocked by firewalls on the same subnet.
- B
Ping sweep with nmap -sn
Why wrong: Nmap -sn uses ICMP echo requests by default, which may be blocked.
- C
TCP SYN ping with nmap -PS
Why wrong: TCP SYN ping can be used but may be filtered; it still uses IP packets.
- D
UDP scan with nmap -sU
Why wrong: UDP scan is for port discovery, not host discovery, and can be unreliable.
Question 183 of 1,000
PT0-002 Practice Question: Information Gathering and Vulnerability Scanning
This PT0-002 practice question tests your understanding of information gathering and vulnerability scanning. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are performing a network scan and need to identify live hosts on a subnet without triggering firewalls that block ICMP. Which technique should you use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ARP scan with arp-scan
Using ARP scan (arp-scan) works on local networks and does not rely on ICMP, making it effective even when ICMP is blocked. It sends ARP requests and listens for replies.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ARP scan with arp-scan
- ✗
Ping sweep with nmap -sn
Why it's wrong here
Nmap -sn uses ICMP echo requests by default, which may be blocked.
- ✗
TCP SYN ping with nmap -PS
Why it's wrong here
TCP SYN ping can be used but may be filtered; it still uses IP packets.
- ✗
UDP scan with nmap -sU
Why it's wrong here
UDP scan is for port discovery, not host discovery, and can be unreliable.
Common exam traps
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.
Detailed technical explanation
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.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PT0-002 subnetting questions on CIDR, address ranges, and subnet selection.
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Information Gathering and Vulnerability Scanning — study guide chapter
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FAQ
Questions learners often ask
What does this PT0-002 question test?
Information Gathering and Vulnerability Scanning — This question tests Information Gathering and Vulnerability Scanning — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: ARP scan with arp-scan — Using ARP scan (arp-scan) works on local networks and does not rely on ICMP, making it effective even when ICMP is blocked. It sends ARP requests and listens for replies.
What should I do if I get this PT0-002 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PT0-002 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jul 4, 2026
This PT0-002 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PT0-002 exam.
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