- A
ARP scan using arp-scan
Correct. ARP scanning is effective for local subnet discovery.
- B
TCP SYN scan on port 80
Why wrong: SYN scan is a port scan, not a host discovery technique, and sends more packets.
- C
UDP scan on port 161
Why wrong: UDP scan targets a specific service, not host discovery.
- D
ICMP ping sweep using nmap -sn
Correct. Ping sweep identifies live hosts with minimal probes.
- E
DNS zone transfer
Why wrong: Zone transfer is for DNS enumeration, not host discovery.
Question 822 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.
A penetration tester is performing reconnaissance on a target network and wants to identify all live hosts without sending many packets. Which TWO techniques are MOST effective for host discovery in a local subnet? (Select TWO.)
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 using arp-scan
ARP scan using arp-scan is effective because it sends ARP requests to every IP in the subnet and listens for ARP replies. Since ARP is a Layer 2 protocol, it does not require IP-level responses and works even if hosts block ICMP or TCP probes. This technique is extremely fast and generates minimal traffic, making it ideal for local subnet host discovery.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 using arp-scan
Why this is correct
Correct. ARP scanning is effective for local subnet discovery.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
TCP SYN scan on port 80
Why it's wrong here
SYN scan is a port scan, not a host discovery technique, and sends more packets.
- ✗
UDP scan on port 161
Why it's wrong here
UDP scan targets a specific service, not host discovery.
- ✓
ICMP ping sweep using nmap -sn
Why this is correct
Correct. Ping sweep identifies live hosts with minimal probes.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
DNS zone transfer
Why it's wrong here
Zone transfer is for DNS enumeration, not host discovery.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often overlook ARP scans because they think only ICMP or TCP techniques are valid for host discovery, but on a local subnet ARP is the most efficient and stealthy method, while ICMP ping sweeps are also correct but can be blocked by host firewalls.
Detailed technical explanation
How to think about this question
ARP operates at Layer 2 and uses broadcast frames (destination MAC FF:FF:FF:FF:FF:FF) to query all devices on the local subnet; each live host responds with its MAC address, providing instant confirmation without IP stack involvement. In contrast, ICMP ping sweeps (nmap -sn) send ICMP echo requests and listen for replies, but some hosts or firewalls may block ICMP, making ARP scans more reliable on the same broadcast domain. A real-world scenario is internal network reconnaissance where stealth is critical, as ARP scans are often not logged by IDS/IPS systems that focus on IP traffic.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ARP scan using arp-scan — ARP scan using arp-scan is effective because it sends ARP requests to every IP in the subnet and listens for ARP replies. Since ARP is a Layer 2 protocol, it does not require IP-level responses and works even if hosts block ICMP or TCP probes. This technique is extremely fast and generates minimal traffic, making it ideal for local subnet host discovery.
What should I do if I get this PT0-002 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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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