220-1101 Hardware and Network Troubleshooting Practice Question
A user reports that their workstation can access the internet but cannot access network shares on the local file server. The technician runs ipconfig and sees IP address 192.168.1.100, subnet mask 255.255.255.0, default gateway 192.168.1.1. The technician successfully pings the gateway and a public IP address (8.8.8.8). However, pinging the file server at 192.168.1.50 fails with 'Request timed out'. Other workstations on the same subnet can access the file server. Which of the following is the MOST likely cause?
⚠ Common exam trap
Test-takers frequently assume a successful ping to the gateway and internet means the entire network stack is healthy, overlooking that a duplicate IP address causes asymmetric communication failures only with specific hosts on the same subnet.
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
✓
The workstation has a duplicate IP address with another device on the network
The workstation can ping the gateway and a public IP, confirming that its IP configuration, subnet mask, and default gateway are correct and that Layer 3 routing works. However, it cannot ping the file server (192.168.1.50) while other workstations on the same subnet can. This points to a local Layer 2 or Layer 3 conflict specific to this workstation. A duplicate IP address would cause the file server's ARP table to map 192.168.1.100 to the wrong MAC address, so pings from this workstation to the file server go unanswered because the file server sends replies to the other device with the same IP.
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 workstation has a duplicate IP address with another device on the network
Why this is correct
A duplicate IP address means another device on the same subnet is using the same IP as the workstation, causing the switch/router's ARP cache to oscilate between two MAC addresses. When the workstation pings the file server, some ICMP echo replies may be sent to the other device, so communication fails despite internet traffic working through the gateway. Because internet-bound packets are routed past the local ARP conflict, their success does not rule out an IP conflict.
- ✗
The subnet mask on the workstation is configured incorrectly
Why it's wrong here
An incorrect subnet mask affects the workstation's decision about whether a destination is local or remote. If the mask were wrong, the workstation would either ARP for the file server when the server is outside the configured subnet, or send packets to the default gateway for a server that is actually local; both scenarios would likely break all local communication, not just the file server. Since the workstation successfully reaches the internet via the gateway, the mask is almost certainly valid for both local and remote destinations.
- ✗
The Windows Firewall is blocking inbound traffic to the file server
Why it's wrong here
The Windows Firewall on the workstation controls inbound traffic destined for the workstation itself; it does not filter outbound traffic that the workstation initiates, such as a ping to a file server. Even if the firewall had restrictive outbound rules, a standard ICMP ping to a local server is typically not blocked by the default Windows Firewall profile. Also, the file server would need its own firewall configured to block ICMP for the ping to be dropped, but that is not what this option describes.
- ✗
The DNS server is not resolving the file server's hostname
Why it's wrong here
The ping command is being issued to an IP address, not a hostname, so the workstation does not invoke DNS resolution. DNS is only used when an application needs to map a fully qualified domain name to a numeric address; a raw IP ping bypasses the resolver entirely. Thus, even if the DNS server were unreachable or misconfigured, it would have no impact on the ping's ability to send ICMP packets directly to the file server's IP.
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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