220-1101 Networking Practice Question
A technician is setting up a small network with a router, a 24-port unmanaged switch, and 15 computers. The router's DHCP server assigns IP addresses in the 192.168.1.0/24 range. All computers get valid IP addresses and can access the internet, but they cannot see each other in the network discovery list. Which of the following is the MOST likely cause?
⚠ Common exam trap
CompTIA often tests the distinction between Layer 3 connectivity (IP, internet access) and Layer 2/application-layer services (network discovery, file sharing), leading candidates to incorrectly blame VLANs or subnet masks when the real issue is a host-based firewall or service setting.
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
✓
Network discovery and file sharing are disabled on the computers
The computers can access the internet and receive valid IP addresses from the router's DHCP server, indicating that Layer 3 connectivity is working. However, they cannot see each other in the network discovery list, which is a Layer 2/application-layer feature. Network discovery relies on the Function Discovery Resource Publication (FDResPub) and SSDP protocols, and file sharing relies on the SMB protocol; both are typically disabled by default on Windows machines for security reasons. Enabling network discovery and file sharing in the Network and Sharing Center resolves the visibility issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The switch is not configured with VLANs
Why it's wrong here
An unmanaged switch is a plug-and-play device with no management interface, so it cannot have VLANs configured; it operates as a single broadcast domain. All ports on the switch are in the same default VLAN, which is exactly the behavior required for normal peer discovery and file sharing. The absence of VLAN configuration is not a fault, and even a managed switch with VLANs would need to be deliberately set to separate ports to block visibility—an unmanaged switch cannot do this.
When this WOULD be correct
A technician sets up a network with a managed switch and multiple VLANs for security. Computers on different VLANs cannot see each other in network discovery, and the question asks for the most likely cause.
- ✓
Network discovery and file sharing are disabled on the computers
Why this is correct
Network discovery is a Windows service that controls whether the computer broadcasts and listens for discovery messages via the Function Discovery Resource Publication service. When disabled, the system does not appear in the Network folder, and the Windows Firewall may also block file-sharing ports (SMB 445) on Public profiles. Even though all devices share the same subnet, the user-facing symptom of "not seeing each other" in File Explorer is exactly the result of this default off setting.
- ✗
The subnet mask is set to 255.255.0.0
Why it's wrong here
The DHCP server on the router assigns a /24 mask (255.255.255.0), putting all 192.168.1.x devices in the same subnet, which is correct for local communication. If a client were configured with the larger /16 mask (255.255.0.0), it would still treat the destination address as local and would actually broaden the broadcast domain; it would not prevent communication. Thus, the subnet mask is not a factor in why the computers cannot discover each other.
When this WOULD be correct
A technician sets up a network with two separate subnets (e.g., 192.168.1.0/24 and 192.168.2.0/24) but mistakenly configures all devices with a subnet mask of 255.255.0.0. Devices on different subnets cannot communicate directly, causing connectivity issues.
- ✗
The router's firewall is blocking LAN traffic
Why it's wrong here
The router's SPI firewall is designed to protect the LAN from unsolicited inbound traffic originating from the WAN interface; it does not inspect or filter traffic that stays within the LAN, such as a packet sent from one PC to another via the switch. Inter-LAN communication is forwarded at Layer 2 by the switch and only reaches the router if it must go to a different subnet or the router itself. Therefore, the router's firewall is not involved in blocking LAN peer-to-peer visibility.
When this WOULD be correct
In a scenario where computers on the same LAN cannot communicate with each other (e.g., cannot ping or access shared resources) but have internet access, and the router has a firewall setting that blocks inter-VLAN or LAN traffic, such as a 'Client Isolation' or 'AP Isolation' feature enabled.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓Network discovery and file sharing are disabled on the computersCorrect answer▾
Why this is correct
Network discovery is a Windows service that controls whether the computer broadcasts and listens for discovery messages via the Function Discovery Resource Publication service. When disabled, the system does not appear in the Network folder, and the Windows Firewall may also block file-sharing ports (SMB 445) on Public profiles. Even though all devices share the same subnet, the user-facing symptom of "not seeing each other" in File Explorer is exactly the result of this default off setting.
✗The switch is not configured with VLANsWrong answer — click to see why▾
Why this is wrong here
The switch is unmanaged, so it cannot be configured with VLANs. VLANs require a managed switch, and even if VLANs were present, they would not prevent devices on the same subnet from seeing each other unless configured to isolate ports.
★ When this WOULD be the correct answer
A technician sets up a network with a managed switch and multiple VLANs for security. Computers on different VLANs cannot see each other in network discovery, and the question asks for the most likely cause.
Why candidates choose this
Candidates may confuse unmanaged switches with managed ones and think VLAN misconfiguration is a common cause of network discovery issues, not realizing that unmanaged switches lack VLAN support.
✗The subnet mask is set to 255.255.0.0Wrong answer — click to see why▾
Why this is wrong here
The subnet mask 255.255.0.0 would place all 192.168.1.x addresses in the same subnet (192.168.0.0/16), so it would not prevent network discovery. The issue is that network discovery is disabled on the computers, not a subnet mismatch.
★ When this WOULD be the correct answer
A technician sets up a network with two separate subnets (e.g., 192.168.1.0/24 and 192.168.2.0/24) but mistakenly configures all devices with a subnet mask of 255.255.0.0. Devices on different subnets cannot communicate directly, causing connectivity issues.
Why candidates choose this
Candidates may think an incorrect subnet mask could isolate devices, but here the mask is too large (not too small), so it would actually broaden the subnet and not cause isolation.
✗The router's firewall is blocking LAN trafficWrong answer — click to see why▾
Why this is wrong here
The router's firewall typically blocks inbound traffic from the WAN, not LAN-to-LAN traffic. Since computers can access the internet and get valid IPs, the firewall is not interfering with local network discovery.
★ When this WOULD be the correct answer
In a scenario where computers on the same LAN cannot communicate with each other (e.g., cannot ping or access shared resources) but have internet access, and the router has a firewall setting that blocks inter-VLAN or LAN traffic, such as a 'Client Isolation' or 'AP Isolation' feature enabled.
Why candidates choose this
Candidates may assume that any network issue involving connectivity is due to a firewall, especially when internet access works but local communication fails, without considering that firewalls typically only filter traffic crossing network boundaries.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Wireless Security: WEP, WPA, WPA2, WPA3
Key term
SMB
SMB is a network file-sharing protocol that allows applications to read, write, and request services from server programs in a computer network.
Key term
Universal Plug and Play
Universal Plug and Play is a set of networking protocols that allows devices on a network to discover each other and connect automatically without manual configuration.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.