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200-901 A company has multiple subnets Practice Question
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?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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.
Answer analysis
Option-by-option breakdown
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
A DNS server resolves names to addresses; it does not forward packets between subnets. Communication across 192.168.1.0/24 and 192.168.2.0/24 requires a router or Layer 3 gateway with routes for both networks. DNS is the right choice only when clients must resolve hostnames rather than reach them by IP.
- ✗
A VLAN
Why it's wrong here
A VLAN logically segments a single switch into separate broadcast domains; it does not route packets between the 192.168.1.0/24 and 192.168.2.0/24 networks. VLANs are tempting because they separate subnets, but inter-subnet traffic still requires a router or layer-3 switch.
- ✗
A bridge
Why it's wrong here
A bridge forwards frames within one broadcast domain; these subnets are separate layer-3 networks, so traffic needs a router (or layer-3 switch) to forward between them. Bridging is tempting because it connects segments, but it operates at layer 2 and cannot route between distinct IP subnets.
- ✓
A router or Layer 3 switch
Why this is correct
A router or Layer 3 switch performs inter-subnet routing, forwarding packets between the 192.168.1.0/24 and 192.168.2.0/24 broadcast domains. Since these are distinct IP subnets, Layer 2 switching alone cannot bridge them; a Layer 3 device is required to satisfy the cross-subnet communication constraint.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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