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 unauthorized DHCP servers from offering IP addresses to clients on a switch. Which security feature should be enabled?
Why wrong: BPDU guard protects against Bridge Protocol Data Unit (BPDU) manipulation, typically used to prevent rogue switches from participating in STP. It does not affect DHCP servers.
B
DHCP snooping
DHCP snooping inspects DHCP traffic and allows only authorized DHCP servers on trusted ports, blocking any DHCP offers from untrusted ports.
C
Dynamic ARP inspection
Why wrong: DAI validates ARP packets to prevent ARP spoofing attacks, but it does not directly block DHCP servers.
D
Port security
Why wrong: Port security limits the number of MAC addresses allowed on a port, preventing MAC flooding but not rogue DHCP servers.
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 answer because it is a security feature specifically designed to filter untrusted DHCP messages on a switch. By configuring trusted and untrusted ports, DHCP snooping drops DHCP server responses (OFFER, ACK) received on untrusted ports, effectively preventing rogue DHCP servers from assigning IP addresses to clients.
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.
✗
BPDU guard
Why it's wrong here
BPDU guard protects against Bridge Protocol Data Unit (BPDU) manipulation, typically used to prevent rogue switches from participating in STP. It does not affect DHCP servers.
✓
DHCP snooping
Why this is correct
DHCP snooping inspects DHCP traffic and allows only authorized DHCP servers on trusted ports, blocking any DHCP offers from untrusted ports.
Related concept
Read the scenario before looking for a memorised answer.
✗
Dynamic ARP inspection
Why it's wrong here
DAI validates ARP packets to prevent ARP spoofing attacks, but it does not directly block DHCP servers.
✗
Port security
Why it's wrong here
Port security limits the number of MAC addresses allowed on a port, preventing MAC flooding but not rogue DHCP servers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse DHCP snooping with Dynamic ARP Inspection, but DAI only validates ARP traffic, not DHCP offers, while BPDU guard is an STP mechanism unrelated to DHCP security.
Detailed technical explanation
How to think about this question
DHCP snooping operates by maintaining a DHCP snooping binding table that maps client MAC addresses, IP addresses, VLANs, and port information. When a DHCP server response arrives on an untrusted port, the switch compares it against the table and drops the packet if no corresponding client request (DISCOVER) was seen, or if the server is not on a trusted port. In real-world deployments, uplink ports to legitimate DHCP servers are configured as trusted, while all access ports are untrusted by default.
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 answer because it is a security feature specifically designed to filter untrusted DHCP messages on a switch. By configuring trusted and untrusted ports, DHCP snooping drops DHCP server responses (OFFER, ACK) received on untrusted ports, effectively preventing rogue DHCP servers from assigning IP addresses to clients.
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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