- A
Dynamic ARP Inspection (DAI)
Why wrong: DAI protects against ARP spoofing, not rogue DHCP servers.
- B
IP Source Guard
Why wrong: IP Source Guard prevents IP spoofing by filtering traffic based on DHCP snooping bindings, but does not directly block rogue DHCP servers.
- C
DHCP Snooping
DHCP Snooping allows only DHCP messages from trusted DHCP servers, blocking unauthorized DHCP offers.
- D
Port Security
Why wrong: Port Security limits the number of MAC addresses on a port but does not filter DHCP messages.
Question 5 of 520
N10-009 Network Security Practice Question
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 is experiencing issues where unauthorized devices are offering IP addresses to clients, causing connectivity problems. Which security feature should be enabled on switches to prevent this?
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
✓
DHCP Snooping
C is correct because DHCP Snooping is a security feature that filters untrusted DHCP messages on a per-port basis, preventing unauthorized DHCP servers from offering IP addresses to clients. By configuring trusted ports (typically uplinks to legitimate DHCP servers) and untrusted ports (access ports), the switch drops DHCPOFFER and DHCPACK messages received on untrusted ports, directly stopping rogue DHCP server attacks.
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.
- ✗
Dynamic ARP Inspection (DAI)
When this WOULD be correct
DAI would be correct in a scenario where the network is experiencing ARP spoofing attacks, where an attacker sends forged ARP replies to associate their MAC address with the IP address of a legitimate device, causing traffic interception.
- ✗
IP Source Guard
Why it's wrong here
IP Source Guard prevents IP spoofing by filtering traffic based on DHCP snooping bindings, but does not directly block rogue DHCP servers.
When this WOULD be correct
A network administrator notices clients are receiving IP addresses from unknown sources and suspects IP spoofing attacks. Enabling IP Source Guard on access ports would block traffic from unauthorized IP addresses.
- ✓
DHCP Snooping
Why this is correct
DHCP Snooping allows only DHCP messages from trusted DHCP servers, blocking unauthorized DHCP offers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Port Security
Why it's wrong here
Port Security limits the number of MAC addresses on a port but does not filter DHCP messages.
When this WOULD be correct
A question asking which feature prevents MAC flooding attacks or restricts device access based on MAC addresses on a switch port would make Port Security the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓DHCP SnoopingCorrect answer▾
Why this is correct
DHCP Snooping allows only DHCP messages from trusted DHCP servers, blocking unauthorized DHCP offers.
✗Dynamic ARP Inspection (DAI)Wrong answer — click to see why▾
Why this is wrong here
Dynamic ARP Inspection (DAI) validates ARP packets to prevent man-in-the-middle attacks, but it does not prevent unauthorized DHCP servers from offering IP addresses. The issue described is rogue DHCP servers, which DHCP Snooping addresses.
★ When this WOULD be the correct answer
DAI would be correct in a scenario where the network is experiencing ARP spoofing attacks, where an attacker sends forged ARP replies to associate their MAC address with the IP address of a legitimate device, causing traffic interception.
Why candidates choose this
Candidates may confuse DAI with DHCP Snooping because both are security features that rely on DHCP Snooping's binding database, and both protect against different types of attacks on the same layer.
✗IP Source GuardWrong answer — click to see why▾
Why this is wrong here
IP Source Guard prevents IP spoofing by filtering traffic based on DHCP snooping bindings, but it does not prevent unauthorized DHCP servers from offering IP addresses.
★ When this WOULD be the correct answer
A network administrator notices clients are receiving IP addresses from unknown sources and suspects IP spoofing attacks. Enabling IP Source Guard on access ports would block traffic from unauthorized IP addresses.
Why candidates choose this
Candidates may confuse IP Source Guard with DHCP Snooping because both rely on DHCP snooping bindings, but they address different threats: IP Source Guard filters IP traffic, while DHCP Snooping filters DHCP messages.
✗Port SecurityWrong answer — click to see why▾
Why this is wrong here
Port Security limits the number of MAC addresses per port but does not prevent unauthorized DHCP servers from offering IP addresses.
★ When this WOULD be the correct answer
A question asking which feature prevents MAC flooding attacks or restricts device access based on MAC addresses on a switch port would make Port Security the correct answer.
Why candidates choose this
Candidates may confuse port-level security with DHCP protection, thinking that restricting MAC addresses also blocks rogue DHCP servers.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the roles of DHCP Snooping, DAI, and IP Source Guard, often selecting DAI because they associate ARP with address assignment, but only DHCP Snooping directly filters unauthorized DHCP server messages.
Detailed technical explanation
How to think about this question
DHCP Snooping builds a binding database (DHCP snooping binding table) that maps client MAC addresses, IP addresses, VLAN, and port information, which is then used by DAI and IP Source Guard for additional security. In a real-world scenario, an attacker could plug a consumer router into an access port; DHCP Snooping would drop its DHCPOFFER messages because the port is untrusted, while DAI alone would not catch this attack.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this N10-009 question test?
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 — C is correct because DHCP Snooping is a security feature that filters untrusted DHCP messages on a per-port basis, preventing unauthorized DHCP servers from offering IP addresses to clients. By configuring trusted ports (typically uplinks to legitimate DHCP servers) and untrusted ports (access ports), the switch drops DHCPOFFER and DHCPACK messages received on untrusted ports, directly stopping rogue DHCP server attacks.
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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Last reviewed: Jun 11, 2026
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