The answer is DHCP snooping, which is the correct security feature to prevent a rogue DHCP server from assigning IP addresses on your network. This works by configuring switch ports as either trusted or untrusted: trusted ports are reserved for legitimate DHCP servers, while all client-facing ports are untrusted. When DHCP snooping is enabled, the switch inspects all DHCP messages and automatically drops any DHCPOFFER, DHCPACK, or DHCPNAK packets received on untrusted ports, effectively blocking unauthorized devices from handing out IP addresses. On the CompTIA Network+ N10-009 exam, this concept tests your understanding of Layer 2 security mechanisms and often appears alongside ARP inspection or dynamic ARP inspection as a related countermeasure. A common trap is confusing DHCP snooping with DHCP starvation attacks—remember, snooping blocks rogue *servers*, while starvation attacks exhaust the DHCP pool. For a quick memory tip, think “trust the server, snoop the client”: only allow DHCP offers from ports you explicitly trust.
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 discovers that client workstations are receiving IP addresses from an unknown device, causing network connectivity issues. Which security feature should be configured on switches to prevent rogue DHCP servers from assigning IP addresses?
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. By configuring ports as trusted (where legitimate DHCP servers are connected) and untrusted (client-facing ports), the switch drops all DHCP server messages (OFFER, ACK, NAK) received on untrusted ports, effectively blocking rogue DHCP servers from assigning IP addresses.
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 filters DHCP traffic and allows only trusted DHCP servers, preventing rogue DHCP servers from assigning IP addresses.
Related concept
Read the scenario before looking for a memorised answer.
Port security limits the number of MAC addresses on a port but does not prevent rogue DHCP servers.
✗
BPDU guard
Why it's wrong here
BPDU guard disables a port if it receives a BPDU, protecting against rogue switches 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 (DAI) because both rely on the DHCP snooping binding table, but DAI only validates ARP packets, not DHCP server messages.
Detailed technical explanation
How to think about this question
DHCP snooping builds a DHCP snooping binding table by monitoring DHCPACK messages from trusted servers, mapping client MAC, IP, VLAN, port, and lease time. This table is then used by Dynamic ARP Inspection (DAI) and IP Source Guard to enforce IP-to-MAC bindings. In a real-world scenario, a misconfigured home router plugged into an access port can act as a rogue DHCP server; DHCP snooping drops its OFFER messages, preventing IP address conflicts and connectivity loss.
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. By configuring ports as trusted (where legitimate DHCP servers are connected) and untrusted (client-facing ports), the switch drops all DHCP server messages (OFFER, ACK, NAK) received on untrusted ports, effectively blocking rogue DHCP servers from assigning IP addresses.
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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