Quick Answer
The answer is `nmap -sn 192.168.1.0/24`, as the `-sn` flag specifically performs a ping sweep for host discovery without initiating port scans or OS detection. This command efficiently identifies live hosts on a /24 subnet by sending a default combination of probes—ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests—allowing the tester to quickly map active devices while minimizing network overhead. On the Certified Ethical Hacker CEH exam, this tests your understanding of Nmap’s host discovery phase versus full scan types; a common trap is confusing `-sn` with `-sP` (deprecated but still recognized) or assuming a ping sweep requires the `-PE` flag alone. Remember the memory tip: “-sn means scan no ports”—it’s the go-to command for a silent, efficient sweep that answers the question “who’s alive?” without the noise of a full port scan.
This CEH practice question tests your understanding of footprinting, reconnaissance and 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 wants to perform a ping sweep on a /24 subnet to identify live hosts. Which command would accomplish this efficiently?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
nmap -sn 192.168.1.0/24
-sn is the Nmap ping sweep flag that discovers live hosts without scanning ports.
nmap -O 192.168.1.0/24
Why wrong: -O performs OS fingerprinting, not a ping sweep.
nmap -p- 192.168.1.0/24
Why wrong: -p- scans all 65535 TCP ports on each host, which is heavy and not a ping sweep.
nmap -sV 192.168.1.0/24
Why wrong: -sV performs version detection on open ports, not a ping sweep.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
nmap -sn 192.168.1.0/24
Option A is correct because `nmap -sn` performs a ping sweep (host discovery) without port scanning, sending ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests by default. This efficiently identifies live hosts on a /24 subnet without the overhead of port scanning or OS detection.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
nmap -sn 192.168.1.0/24
Why this is correct
-sn is the Nmap ping sweep flag that discovers live hosts without scanning ports.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
nmap -O 192.168.1.0/24
Why it's wrong here
-O performs OS fingerprinting, not a ping sweep.
nmap -p- 192.168.1.0/24
Why it's wrong here
-p- scans all 65535 TCP ports on each host, which is heavy and not a ping sweep.
nmap -sV 192.168.1.0/24
Why it's wrong here
-sV performs version detection on open ports, not a ping sweep.
Common exam traps
The trap here is that candidates often confuse `-sn` (ping sweep) with `-sP` (deprecated alias) or assume that `-O` or `-sV` are faster because they provide more information, but they actually add significant overhead and are not designed for simple host discovery.
Detailed technical explanation
The `-sn` flag in Nmap disables port scanning and uses a combination of ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests to determine if a host is alive. On a local network, it also sends ARP requests, which are more reliable for host discovery. This approach minimizes network traffic and time, making it ideal for scanning large subnets like /24 (256 IPs) in seconds.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
The correct answer is: nmap -sn 192.168.1.0/24 — Option A is correct because `nmap -sn` performs a ping sweep (host discovery) without port scanning, sending ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests by default. This efficiently identifies live hosts on a /24 subnet without the overhead of port scanning or OS detection.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This CEH practice question is part of Courseiva's free EC-Council 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 CEH exam.
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