The correct answer is the ping sweep using `nmap -sn`, as this scan type is specifically designed for efficient host discovery by sending a minimal set of probe packets—ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests—to determine which hosts are alive on a subnet like 192.168.1.0/24 without performing a full port scan. This minimizes network traffic because it avoids sending packets to every IP individually or probing all 65,535 ports, making it the ideal choice when the goal is simply to identify active devices. On the Certified Ethical Hacker CEH exam, this concept tests your understanding of reconnaissance phases and Nmap’s host discovery options, often appearing as a scenario where you must balance stealth with efficiency. A common trap is confusing `-sn` with a full TCP connect scan (`-sT`) or a SYN scan (`-sS`), which generate far more traffic. Remember the mnemonic: “SN means ‘Show Neighbors’—just a quick ping, not a deep dive.”
CEH Scanning Networks and Enumeration Practice Question
This CEH practice question tests your understanding of scanning networks and enumeration. 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 security analyst is using Nmap to scan a network segment 192.168.1.0/24 and wants to identify live hosts without sending packets to every IP. Which scan type should the analyst use to minimize network traffic while discovering active hosts?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Ping sweep using `nmap -sn`
Option C is correct because `nmap -sn` (ping sweep) sends ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests by default, allowing the analyst to discover live hosts without scanning every port or sending packets to every IP individually. This minimizes network traffic compared to full port scans while still efficiently identifying active devices on the 192.168.1.0/24 subnet.
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.
✗
TCP SYN scan using `nmap -sS`
Why it's wrong here
SYN scan probes ports, not just host discovery; generates more traffic.
✗
ARP scan using `nmap -PR`
Why it's wrong here
ARP scan is fast but sends ARP requests to every IP, which is still per-IP traffic.
✓
Ping sweep using `nmap -sn`
Why this is correct
`-sn` disables port scan and sends only ICMP echo, TCP SYN to port 443, etc., minimizing traffic.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
UDP scan using `nmap -sU`
Why it's wrong here
UDP scan is slow and often unreliable for host discovery.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'minimizing network traffic' with using a stealth scan like `-sS`, but the question specifically asks for host discovery, not port scanning, and `-sn` is the correct low-traffic option for that purpose.
Detailed technical explanation
How to think about this question
The `-sn` flag in Nmap uses a multi-method discovery approach: it sends ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests, then considers a host alive if any response is received. This behavior is defined in Nmap's host discovery algorithm, which can be customized with options like `-PE`, `-PP`, or `-PM` to override defaults. In real-world scenarios, firewalls may block ICMP, but the TCP probes often bypass such filters, making `-sn` more reliable than a simple ping sweep.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Scanning Networks and Enumeration — This question tests Scanning Networks and Enumeration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Ping sweep using `nmap -sn` — Option C is correct because `nmap -sn` (ping sweep) sends ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests by default, allowing the analyst to discover live hosts without scanning every port or sending packets to every IP individually. This minimizes network traffic compared to full port scans while still efficiently identifying active devices on the 192.168.1.0/24 subnet.
What should I do if I get this CEH question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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