The answer is to configure an ACL on the Layer 3 switch to permit specific traffic between VLANs. This is correct because a Layer 3 switch uses a Switch Virtual Interface (SVI) as the routed gateway for each VLAN, and an ACL applied to that SVI can filter inter-VLAN traffic at Layer 3, allowing you to permit only the HR subnet’s traffic to the printer’s IP address while denying all other cross-VLAN communication. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of policy-based segmentation—a common trap is thinking a Layer 2 ACL or VLAN access-map alone will work, but inter-VLAN filtering requires Layer 3 inspection on the routed interface. Remember the key distinction: ACLs on a Layer 3 switch filter traffic between VLANs, not within them. A helpful memory tip is “SVIs need ACLs for inter-VLAN control”—if traffic must cross VLANs, the filter goes on the SVI.
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.
An organization has separate VLANs for the HR and Finance departments. Both VLANs use a single Layer 3 switch to route between them. The HR department needs access to a shared printer located in the Finance VLAN, but all other traffic between the VLANs should be blocked. Which of the following should be configured?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure an ACL on the Layer 3 switch to permit specific traffic between VLANs
An ACL on the Layer 3 switch can filter inter-VLAN traffic at the routed interface (SVI or routed port). By permitting only the HR subnet’s traffic to the printer’s IP address and denying all other inter-VLAN traffic, you meet the requirement of selective access while blocking everything else. This is the standard method for policy-based segmentation between VLANs.
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.
✓
Configure an ACL on the Layer 3 switch to permit specific traffic between VLANs
Why this is correct
Correct. ACLs on the Layer 3 switch can filter inter-VLAN traffic to allow only the required printer access.
Related concept
Read the scenario before looking for a memorised answer.
✗
Place the printer in the HR VLAN
Why it's wrong here
Moving the printer to HR VLAN would give full access, but the requirement is to keep it in Finance VLAN.
✗
Create a separate VLAN for the printer
Why it's wrong here
A separate VLAN would still require routing and ACLs to control access; not the simplest solution.
✗
Use a wireless access point to bridge the VLANs
Why it's wrong here
Wireless bridges do not provide granular filtering and would not meet security requirements.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think placing the printer in the same VLAN or creating a dedicated VLAN solves the problem, but they overlook that ACLs are the precise tool for granular, policy-based filtering between VLANs on a Layer 3 switch.
Detailed technical explanation
How to think about this question
On a Layer 3 switch, inter-VLAN routing occurs through switched virtual interfaces (SVIs) or routed ports. An ACL applied inbound or outbound on the SVI for the HR VLAN can match source IPs from HR and destination IP/port for the printer (e.g., TCP 9100 for raw printing), using a permit statement, followed by an implicit deny all. This leverages hardware-accelerated ACL processing in the switch ASIC, ensuring line-rate filtering without performance degradation.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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: Configure an ACL on the Layer 3 switch to permit specific traffic between VLANs — An ACL on the Layer 3 switch can filter inter-VLAN traffic at the routed interface (SVI or routed port). By permitting only the HR subnet’s traffic to the printer’s IP address and denying all other inter-VLAN traffic, you meet the requirement of selective access while blocking everything else. This is the standard method for policy-based segmentation between VLANs.
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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