- A
Create two separate subnets and connect each department to a different physical switch
Why wrong: This would require additional hardware (another switch) and does not utilize the single managed switch; VLANs are more efficient.
- B
Configure VLANs on the switch and set up a trunk port to the router with subinterfaces
VLANs isolate traffic, and the trunk with subinterfaces (router-on-a-stick) allows the router to route between VLANs and to the internet.
- C
Assign static IPs to all devices and enable MAC address filtering on the switch
Why wrong: MAC filtering controls which devices connect but does not segment traffic; all devices would still be on the same broadcast domain.
- D
Use a firewall between the two departments and disable inter-VLAN routing
Why wrong: This adds complexity and cost; VLANs with proper routing policies are the standard method for segmentation on a single switch.
How to Segment Departments with VLANs and Router-on-a-Stick
This 220-1201 practice question tests your understanding of network configuration 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 administrator needs to segment traffic between the accounting and HR departments to prevent unauthorized access, while still allowing both to reach the internet. The company uses a single managed switch and a router. Which configuration approach meets these requirements?
Quick Answer
The correct choice is to configure VLANs on the switch and set up a trunk port to the router with subinterfaces. This approach achieves VLAN segmentation for department isolation by logically separating accounting and HR traffic on the same physical switch, preventing unauthorized access between them, while the trunk port carries those multiple VLANs to the router. The router then uses subinterfaces—one per VLAN—in a router-on-a-stick configuration to route traffic between departments and out to the internet. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of how VLANs and trunking work together to solve a real-world network security need without adding extra hardware. A common trap is thinking a second switch or separate router ports are required, but a single managed switch and one trunk link are sufficient. Memory tip: think of the trunk as a highway carrying multiple lanes (VLANs), and the router’s subinterfaces as the on-ramps that keep each lane’s traffic separate until routing is needed.
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
Configure VLANs on the switch and set up a trunk port to the router with subinterfaces
Option B is correct because VLANs logically segment traffic between departments on a single switch, and configuring a trunk port to the router with subinterfaces (using VLAN tagging) allows inter-VLAN routing for internet access while maintaining isolation between the accounting and HR VLANs. This approach meets the requirement of preventing unauthorized access between departments while enabling shared internet connectivity through the router.
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.
- ✗
Create two separate subnets and connect each department to a different physical switch
Why it's wrong here
This would require additional hardware (another switch) and does not utilize the single managed switch; VLANs are more efficient.
- ✓
Configure VLANs on the switch and set up a trunk port to the router with subinterfaces
Why this is correct
VLANs isolate traffic, and the trunk with subinterfaces (router-on-a-stick) allows the router to route between VLANs and to the internet.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Assign static IPs to all devices and enable MAC address filtering on the switch
Why it's wrong here
MAC filtering controls which devices connect but does not segment traffic; all devices would still be on the same broadcast domain.
- ✗
Use a firewall between the two departments and disable inter-VLAN routing
Why it's wrong here
This adds complexity and cost; VLANs with proper routing policies are the standard method for segmentation on a single switch.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think VLANs alone provide security without considering that inter-VLAN routing must be explicitly configured on the router to enable internet access, or they may confuse MAC address filtering with network segmentation.
Detailed technical explanation
How to think about this question
Under the hood, 802.1Q VLAN tagging adds a 4-byte tag to Ethernet frames, allowing a single trunk port to carry multiple VLANs; the router’s subinterfaces each terminate a specific VLAN and act as the default gateway for that subnet. In real-world scenarios, this approach scales to hundreds of VLANs, but careful planning of VLAN IDs and IP subnetting is critical to avoid overlap and ensure proper ACLs or firewall rules are applied for security.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Network Configuration Concepts — This question tests Network Configuration Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure VLANs on the switch and set up a trunk port to the router with subinterfaces — Option B is correct because VLANs logically segment traffic between departments on a single switch, and configuring a trunk port to the router with subinterfaces (using VLAN tagging) allows inter-VLAN routing for internet access while maintaining isolation between the accounting and HR VLANs. This approach meets the requirement of preventing unauthorized access between departments while enabling shared internet connectivity through the router.
What should I do if I get this 220-1201 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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Last reviewed: Jul 4, 2026
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