This 200-901 practice question tests your understanding of network fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 company has multiple subnets. A device in subnet 192.168.1.0/24 needs to communicate with a device in subnet 192.168.2.0/24. What is required for this communication?
A DNS server
Why wrong: DNS resolves names to IP addresses but does not provide routing.
A VLAN
Why wrong: VLANs segment a network at Layer 2 but do not route between subnets.
A bridge
Why wrong: Bridges operate at Layer 2 and only connect the same subnet.
A router or Layer 3 switch
A router or Layer 3 switch can forward packets between different subnets.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
A router or Layer 3 switch
Devices in different subnets (192.168.1.0/24 and 192.168.2.0/24) are on separate Layer 3 networks. To forward packets between these subnets, a router or Layer 3 switch is required to perform IP routing, using the destination IP address to determine the next hop. Without a Layer 3 device, the frames cannot leave the local broadcast domain.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
A DNS server
Why it's wrong here
DNS resolves names to IP addresses but does not provide routing.
A VLAN
Why it's wrong here
VLANs segment a network at Layer 2 but do not route between subnets.
A bridge
Why it's wrong here
Bridges operate at Layer 2 and only connect the same subnet.
A router or Layer 3 switch
Why this is correct
A router or Layer 3 switch can forward packets between different subnets.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the misconception that a VLAN alone enables communication between subnets, but VLANs only isolate traffic at Layer 2; a Layer 3 device is always needed to route between different subnets.
Detailed technical explanation
When a host in 192.168.1.0/24 sends a packet to 192.168.2.0/24, it checks its routing table and sees the destination is not local, so it forwards the packet to its configured default gateway. The router or Layer 3 switch then performs a longest-prefix match lookup in its routing table (using protocols like OSPF or static routes) and rewrites the Layer 2 header for the next hop. In a real-world scenario, a multilayer switch with switched virtual interfaces (SVIs) can route between VLANs without an external router, but the core requirement remains Layer 3 forwarding.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: A router or Layer 3 switch — Devices in different subnets (192.168.1.0/24 and 192.168.2.0/24) are on separate Layer 3 networks. To forward packets between these subnets, a router or Layer 3 switch is required to perform IP routing, using the destination IP address to determine the next hop. Without a Layer 3 device, the frames cannot leave the local broadcast domain.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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