Quick Answer
The correct answer is to discover SNMP services running on the target. This is because the `-sU` flag forces Nmap to perform a UDP scan, which is essential since SNMP operates exclusively over the User Datagram Protocol, and the `-p 161,162` targets the default ports for SNMP queries and traps. On the Certified Ethical Hacker CEH exam, this command tests your understanding of service discovery techniques and the distinction between TCP and UDP scanning, as many candidates mistakenly apply TCP-based scans to UDP-dependent services like SNMP. A common trap is forgetting that SNMP uses UDP, not TCP, so a standard TCP SYN scan would miss it entirely. To remember this, think of the mnemonic “SNMP is Unreliable but Quick,” linking SNMP to UDP’s connectionless nature, and always pair the `-sU` flag with port 161 to probe for SNMP services.
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
An analyst executes 'nmap -sU -p 161,162 10.0.0.1'. What is the primary purpose of this scan?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Detect TCP services on the target
Why wrong: -sU is for UDP, not TCP.
Enumerate all open ports on the target
Why wrong: Only two specific UDP ports are scanned.
Discover SNMP services running on the target
UDP ports 161 (SNMP) and 162 (SNMP trap) are scanned.
Perform a SYN flood attack
Why wrong: SYN flood is a DoS attack, not a scan.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Discover SNMP services running on the target
The `-sU` flag instructs Nmap to perform a UDP scan, and the `-p 161,162` targets the default SNMP ports (UDP 161 for SNMP queries, UDP 162 for SNMP traps). This combination is specifically designed to discover SNMP services running on the target host, as SNMP operates exclusively over UDP. Option C is correct because the command's primary purpose is to probe for SNMP services.
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.
Detect TCP services on the target
Enumerate all open ports on the target
Why it's wrong here
Only two specific UDP ports are scanned.
Discover SNMP services running on the target
Perform a SYN flood attack
Why it's wrong here
SYN flood is a DoS attack, not a scan.
Common exam traps
The trap here is that candidates often confuse `-sU` with TCP scans or assume the command scans all ports, but CEH specifically tests the understanding that `-sU` with `-p 161,162` targets SNMP over UDP, not general port enumeration or attacks.
Detailed technical explanation
SNMP uses UDP due to its connectionless nature, making it lightweight but also susceptible to spoofing. When Nmap sends a UDP probe to port 161, it expects either an ICMP Port Unreachable (closed) or no response (open/filtered); if the target responds with SNMP data, the port is confirmed open. In real-world scenarios, discovering SNMP can reveal system information via default community strings like 'public', which is a common misconfiguration exploited in footprinting.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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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: Discover SNMP services running on the target — The `-sU` flag instructs Nmap to perform a UDP scan, and the `-p 161,162` targets the default SNMP ports (UDP 161 for SNMP queries, UDP 162 for SNMP traps). This combination is specifically designed to discover SNMP services running on the target host, as SNMP operates exclusively over UDP. Option C is correct because the command's primary purpose is to probe for SNMP services.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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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