- A
Configure the router to use DHCP for the guest network.
Why wrong: DHCP only assigns IP addresses; it does not provide isolation. Guests would still be able to communicate with internal devices if they are on the same subnet.
- B
Create a separate VLAN for the guest network and apply an ACL to block traffic to the internal network.
VLANs logically separate traffic, and ACLs on the router can block inter-VLAN communication, ensuring guests cannot access internal resources while still allowing internet access.
- C
Disable the SSID broadcast for the guest network.
Why wrong: Hiding the SSID does not provide security or isolation; it only makes the network less visible. Guests could still access internal devices if on the same network.
- D
Use a wireless access point with a built-in firewall.
Why wrong: While a firewall can help, the question specifies using a single router and switch. The most straightforward solution is VLAN and ACL configuration on the router.
Guest Wireless VLAN Isolation with ACL
This 220-1201 practice question tests your understanding of common networking hardware. 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 is setting up a guest wireless network in a conference room. They want to ensure that guests can access the internet but cannot communicate with internal corporate devices. The network uses a single router and a switch. Which configuration on the router will best achieve this?
Quick Answer
The correct answer is to create a separate VLAN for the guest wireless network and apply an ACL to block traffic to the internal corporate subnet. This works because VLANs logically segment the network at Layer 2, isolating guest traffic into its own broadcast domain, while an access control list (ACL) on the router’s inter-VLAN interface enforces Layer 3 filtering—denying packets destined for the internal IP range while permitting internet-bound traffic. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of network segmentation and security best practices; a common trap is assuming a simple SSID change or a firewall rule on the switch alone will suffice, but without VLAN isolation and ACL enforcement, guests could still reach internal devices via the router’s default routing. Remember the memory tip: “VLAN to divide, ACL to hide”—the VLAN splits the traffic, and the ACL blocks the path to the internal network.
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
Create a separate VLAN for the guest network and apply an ACL to block traffic to the internal network.
Option B is correct because creating a separate VLAN for the guest network isolates guest traffic at Layer 2, and applying an ACL on the router's VLAN interface blocks traffic destined for the internal network while permitting internet-bound traffic. This ensures guests cannot reach internal corporate devices, meeting the security requirement without additional hardware.
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.
- ✗
Configure the router to use DHCP for the guest network.
Why it's wrong here
DHCP only assigns IP addresses; it does not provide isolation. Guests would still be able to communicate with internal devices if they are on the same subnet.
- ✓
Create a separate VLAN for the guest network and apply an ACL to block traffic to the internal network.
Why this is correct
VLANs logically separate traffic, and ACLs on the router can block inter-VLAN communication, ensuring guests cannot access internal resources while still allowing internet access.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Disable the SSID broadcast for the guest network.
Why it's wrong here
Hiding the SSID does not provide security or isolation; it only makes the network less visible. Guests could still access internal devices if on the same network.
- ✗
Use a wireless access point with a built-in firewall.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that disabling SSID broadcast or using DHCP alone provides security, when in fact VLANs with ACLs are required for true network segmentation and access control.
Detailed technical explanation
How to think about this question
VLANs segment the network at Layer 2, creating separate broadcast domains; the router then performs inter-VLAN routing using subinterfaces or SVI (Switch Virtual Interface). ACLs applied to the guest VLAN interface can deny traffic to the internal subnet (e.g., deny ip 192.168.10.0 0.0.0.255 10.0.0.0 0.255.255.255) while permitting all other traffic, effectively enforcing isolation without needing a dedicated firewall appliance.
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?
Common Networking Hardware — This question tests Common Networking Hardware — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a separate VLAN for the guest network and apply an ACL to block traffic to the internal network. — Option B is correct because creating a separate VLAN for the guest network isolates guest traffic at Layer 2, and applying an ACL on the router's VLAN interface blocks traffic destined for the internal network while permitting internet-bound traffic. This ensures guests cannot reach internal corporate devices, meeting the security requirement without additional hardware.
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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