The answer is that a network switch forwards data based on MAC addresses. This is correct because a switch operates at Layer 2 of the OSI model, where it examines the destination MAC address in each incoming frame and consults its MAC address table to forward the frame only to the specific port connected to that device. By doing so, the switch reduces collision domains and improves overall network efficiency, unlike a hub which floods all ports. On the CompTIA Network+ N10-009 exam, this question tests your understanding of network device OSI layer functions, often pairing a switch with Layer 2 and a router with Layer 3. A common trap is confusing a switch with a router—remember, switches use MAC addresses, not IP addresses. A useful memory tip: “Switch sees MAC, Router sees IP.”
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 technician is explaining the role of a network switch to a new employee. Which of the following best describes the primary function of a switch in a local area network?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Why wrong: Forwarding based on IP addresses is the function of a router or a layer 3 switch, not a basic layer 2 switch.
B
It forwards data based on MAC addresses.
A layer 2 switch uses MAC addresses to forward frames to the correct destination port, reducing unnecessary traffic.
C
It connects different networks and performs routing.
Why wrong: Connecting different networks and routing is the primary function of a router, not a switch.
D
It amplifies and repeats the signal to all ports.
Why wrong: Amplifying and repeating the signal to all ports is the function of a hub, which operates at layer 1 and does not make intelligent forwarding decisions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It forwards data based on MAC addresses.
A network switch operates at Layer 2 of the OSI model and uses MAC addresses to make forwarding decisions. When a frame arrives, the switch examines the destination MAC address, looks it up in its MAC address table, and forwards the frame only to the port associated with that address, reducing collision domains and improving network efficiency.
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.
✗
It forwards data based on IP addresses.
Why it's wrong here
Forwarding based on IP addresses is the function of a router or a layer 3 switch, not a basic layer 2 switch.
✓
It forwards data based on MAC addresses.
Why this is correct
A layer 2 switch uses MAC addresses to forward frames to the correct destination port, reducing unnecessary traffic.
Clue confirmation
The clue words "best", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
It connects different networks and performs routing.
Why it's wrong here
Connecting different networks and routing is the primary function of a router, not a switch.
✗
It amplifies and repeats the signal to all ports.
Why it's wrong here
Amplifying and repeating the signal to all ports is the function of a hub, which operates at layer 1 and does not make intelligent forwarding decisions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between Layer 2 switching (MAC addresses) and Layer 3 routing (IP addresses), and the trap here is that candidates confuse the switch's forwarding decision with that of a router, especially when dealing with multilayer switches that can perform both functions.
Detailed technical explanation
How to think about this question
Switches build their MAC address table by learning the source MAC addresses of incoming frames on each port. In a real-world scenario, if a switch receives a frame with an unknown destination MAC, it floods the frame out all ports except the ingress port, a behavior known as unknown unicast flooding. This process is fundamental to how switches dynamically learn network topology without manual configuration.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: It forwards data based on MAC addresses. — A network switch operates at Layer 2 of the OSI model and uses MAC addresses to make forwarding decisions. When a frame arrives, the switch examines the destination MAC address, looks it up in its MAC address table, and forwards the frame only to the port associated with that address, reducing collision domains and improving network efficiency.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best", "primary". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Match each network device to its primary function.
medium
Why : These are essential network devices.
Variation 2. Which device operates at Layer 1 (Physical) of the OSI model and regenerates electrical signals to extend the distance of a network segment?
easy
A.Switch
B.Router
✓ C.Hub
D.Bridge
Why C: A hub operates at Layer 1 (Physical) of the OSI model. It receives incoming electrical signals on one port and regenerates (repeats) those signals out to all other ports, effectively extending the physical reach of a network segment. Unlike switches or routers, it performs no frame inspection or forwarding decisions.
Variation 3. A network device receives a frame on one port and forwards it out to all other ports. The device does not examine the destination MAC address. Which type of device is being described?
easy
A.Switch
✓ B.Hub
C.Bridge
D.Router
Why B: A hub operates at Layer 1 (physical layer) of the OSI model and simply repeats incoming electrical or optical signals out all other ports without any processing of the frame's destination MAC address. This behavior matches the description exactly: the device receives a frame on one port and forwards it out all other ports without examining the MAC address.
Variation 4. Which of the following devices operates at Layer 3 of the OSI model and makes forwarding decisions based on destination IP addresses?
easy
A.Switch
B.Bridge
✓ C.Router
D.Hub
Why C: A router operates at Layer 3 (Network layer) of the OSI model and uses the destination IP address in the packet header to make forwarding decisions. It maintains a routing table (e.g., via OSPF, EIGRP, or static routes) to determine the next-hop interface for each packet, enabling communication between different subnets or VLANs.
Variation 5. Which of the following network devices operates at Layer 1 of the OSI model and forwards all incoming electrical signals to all of its ports?
easy
A.Router
B.Switch
✓ C.Hub
D.Bridge
Why C: A hub operates at Layer 1 (Physical layer) of the OSI model and is a multiport repeater. It regenerates and forwards every incoming electrical signal out of all ports except the incoming port, regardless of the intended destination, because it has no intelligence to process MAC addresses or frames.
Variation 6. Which of the following network devices operates primarily at Layer 2 of the OSI model and uses MAC addresses to forward data?
easy
A.Hub
✓ B.Switch
C.Router
D.Firewall
Why B: A switch operates primarily at Layer 2 (Data Link layer) of the OSI model, forwarding frames based on destination MAC addresses. It builds a MAC address table by learning source MAC addresses from incoming frames and uses this table to make forwarding decisions, reducing collision domains and improving network efficiency.
Variation 7. At which OSI layer does a router primarily operate to make forwarding decisions based on IP addresses?
easy
A.Layer 1 (Physical)
B.Layer 2 (Data Link)
✓ C.Layer 3 (Network)
D.Layer 4 (Transport)
Why C: A router primarily operates at Layer 3 (Network) of the OSI model because it uses logical IP addresses (e.g., IPv4 or IPv6) to make forwarding decisions. The router examines the destination IP address in the packet header, performs a longest-prefix match against its routing table, and determines the next-hop interface. This layer is responsible for end-to-end delivery and path selection across multiple networks.
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Question Discussion
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