This N10-009 practice question tests your understanding of network security. 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.
A network administrator wants to prevent rogue DHCP servers from offering IP addresses to clients on the network. Which security feature should be enabled on the switches?
DHCP snooping examines DHCP traffic and blocks unauthorized DHCP server responses from untrusted ports.
B
Dynamic ARP Inspection (DAI)
Why wrong: DAI validates ARP packets to prevent ARP spoofing, not DHCP server attacks.
C
Port Security
Why wrong: Port Security limits the number of MAC addresses on a port but does not filter DHCP messages.
D
IP Source Guard
Why wrong: IP Source Guard prevents IP spoofing by filtering traffic based on DHCP snooping bindings but is not designed to block rogue DHCP servers directly.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DHCP snooping
DHCP snooping is the correct security feature because it acts as a firewall between untrusted hosts and trusted DHCP servers. It validates DHCP messages by filtering out responses from unauthorized DHCP servers on untrusted ports, preventing rogue servers from offering IP addresses to clients. This is achieved by building and maintaining a DHCP snooping binding database that tracks valid IP-to-MAC address mappings.
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.
✓
DHCP snooping
Why this is correct
DHCP snooping examines DHCP traffic and blocks unauthorized DHCP server responses from untrusted ports.
Related concept
Read the scenario before looking for a memorised answer.
✗
Dynamic ARP Inspection (DAI)
Why it's wrong here
DAI validates ARP packets to prevent ARP spoofing, not DHCP server attacks.
✗
Port Security
Why it's wrong here
Port Security limits the number of MAC addresses on a port but does not filter DHCP messages.
✗
IP Source Guard
Why it's wrong here
IP Source Guard prevents IP spoofing by filtering traffic based on DHCP snooping bindings but is not designed to block rogue DHCP servers directly.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between DHCP snooping and Dynamic ARP Inspection (DAI), where candidates mistakenly choose DAI because they confuse ARP spoofing with rogue DHCP server attacks.
Detailed technical explanation
How to think about this question
DHCP snooping relies on the concept of trusted and untrusted ports; only ports configured as 'trusted' (typically uplinks to legitimate DHCP servers) are allowed to send DHCPOFFER and DHCPACK messages. The switch inspects DHCP packets at Layer 2 and drops any DHCP server responses received on untrusted ports, using the DHCP snooping binding database to track lease information. In real-world scenarios, a rogue DHCP server could be a malicious laptop plugged into an access port, and DHCP snooping would immediately drop its DHCPOFFER packets, preventing IP address conflicts or man-in-the-middle attacks.
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 practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DHCP snooping — DHCP snooping is the correct security feature because it acts as a firewall between untrusted hosts and trusted DHCP servers. It validates DHCP messages by filtering out responses from unauthorized DHCP servers on untrusted ports, preventing rogue servers from offering IP addresses to clients. This is achieved by building and maintaining a DHCP snooping binding database that tracks valid IP-to-MAC address mappings.
What should I do if I get this N10-009 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.
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Question Discussion
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