The answer is a router, because inter-VLAN routing requires Layer 3 forwarding to move traffic between separate broadcast domains. VLANs segment a Layer 2 network, isolating broadcast traffic, but any communication between VLANs must be routed at Layer 3, which only a router can perform. The router receives 802.1Q-tagged frames from a switch, strips the VLAN tag, makes a forwarding decision based on the destination IP address, then re-encapsulates the frame with the correct destination VLAN tag—a process commonly implemented in a router-on-a-stick configuration. On the CompTIA Network+ N10-009 exam, this concept tests your understanding that switches alone cannot route; a common trap is assuming a multilayer switch can replace a router, but the exam often frames the question around a dedicated router for explicit Layer 3 routing. Remember the memory tip: “Switches split, routers connect”—VLANs split the broadcast domain, and a router is the only device that can reconnect them at Layer 3.
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. 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 engineer is designing a network for a large organization. The engineer needs to ensure that broadcast traffic from one VLAN does not propagate to other VLANs while still allowing inter-VLAN communication. Which of the following devices is required to route between VLANs?
Why wrong: Layer 2 switches forward frames based on MAC addresses and do not perform routing; they keep broadcast domains separate but cannot route between them.
B
Router
A router (or a Layer 3 switch acting as a router) can forward traffic between VLANs by performing routing at Layer 3.
C
Bridge
Why wrong: A bridge is a Layer 2 device that connects two network segments, but it does not route between VLANs.
D
Firewall
Why wrong: A firewall can route between VLANs if it has multiple interfaces and routing capabilities, but the primary device for inter-VLAN routing is a router or Layer 3 switch; the question asks for the required device, and a router is the standard answer.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Router
A router is required to route between VLANs because VLANs segment a Layer 2 broadcast domain, and inter-VLAN communication must occur at Layer 3. The router performs routing by receiving frames tagged with the source VLAN, stripping the tag, making a forwarding decision based on the destination IP, and then re-encapsulating the frame with the destination VLAN tag. This process is often implemented using a router-on-a-stick configuration with 802.1Q trunking.
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.
✗
Layer 2 switch
Why it's wrong here
Layer 2 switches forward frames based on MAC addresses and do not perform routing; they keep broadcast domains separate but cannot route between them.
✓
Router
Why this is correct
A router (or a Layer 3 switch acting as a router) can forward traffic between VLANs by performing routing at Layer 3.
Related concept
Read the scenario before looking for a memorised answer.
✗
Bridge
Why it's wrong here
A bridge is a Layer 2 device that connects two network segments, but it does not route between VLANs.
✗
Firewall
Why it's wrong here
A firewall can route between VLANs if it has multiple interfaces and routing capabilities, but the primary device for inter-VLAN routing is a router or Layer 3 switch; the question asks for the required device, and a router is the standard answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a Layer 3 switch with a Layer 2 switch and assume any switch can route between VLANs, but a standard Layer 2 switch lacks the routing engine and IP forwarding table required for inter-VLAN communication.
Detailed technical explanation
How to think about this question
Inter-VLAN routing requires the router to maintain separate subinterfaces for each VLAN on a single physical interface, each configured with an IP address in the respective VLAN's subnet and encapsulated with 802.1Q tags. The router uses its routing table to forward packets between these subinterfaces, and it must also handle ARP requests within each VLAN without leaking them across VLANs. In real-world scenarios, a Layer 3 switch is often preferred over a router for inter-VLAN routing because it performs hardware-based switching at wire speed, whereas a router typically uses software-based forwarding.
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.
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Router — A router is required to route between VLANs because VLANs segment a Layer 2 broadcast domain, and inter-VLAN communication must occur at Layer 3. The router performs routing by receiving frames tagged with the source VLAN, stripping the tag, making a forwarding decision based on the destination IP, and then re-encapsulating the frame with the destination VLAN tag. This process is often implemented using a router-on-a-stick configuration with 802.1Q trunking.
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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