- A
Disable the local firewall on the workstation to allow all outbound traffic.
Why wrong: While a firewall could block traffic, it is not the most likely cause since DNS queries succeed. Disabling the firewall is a security risk and not a targeted solution.
- B
Renew the DHCP lease to obtain a new IP address.
Why wrong: Renewing DHCP may not resolve the issue since the IP configuration appears correct and DNS is reachable.
- C
Restart the network interface card (NIC) to reset the connection.
Why wrong: Restarting the NIC might temporarily reset the connection, but it doesn't address the root cause of routing to the API subnet.
- D
Check the default gateway configuration. Ensure it is set to 192.168.1.1 and that the gateway can route traffic to the API's subnet.
The default gateway is likely missing or misconfigured, preventing traffic to the API subnet. Verifying its setting and reachability resolves the issue.
200-901 Network Fundamentals Practice Question
This 200-901 practice question tests your understanding of network fundamentals. 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 developer is trying to access an internal corporate web API at http://api.internal.company.com from their workstation, which has the IP configuration: IP address 192.168.1.100, subnet mask 255.255.255.0, default gateway 192.168.1.1, and DNS server 192.168.1.2. The developer can ping the DNS server (192.168.1.2) successfully, but when they try to curl the API endpoint, the command times out. The developer also confirms that the API server is up and reachable from other devices on the same subnet. Which action should the developer take to resolve this issue?
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
Check the default gateway configuration. Ensure it is set to 192.168.1.1 and that the gateway can route traffic to the API's subnet.
The issue is that the DNS resolution is likely failing for the internal domain. Since the developer can successfully reach the DNS server, the problem might be a missing DNS record or a misconfigured search domain. However, the correct action is to first verify the DNS resolver configuration, which is already given. Actually, let's re-think: The developer can ping the DNS server but curl times out. The API server is reachable from other devices. The developer's workstation is on the same subnet as the gateway? Actually, the API server is on the same subnet as other devices, but the developer is on a different subnet? The scenario states other devices on the same subnet can reach the API. The developer might have a wrong default gateway. The correct action is to check the default gateway. However, if the default gateway is wrong, pinging the DNS server might still work if it's on the same subnet? But DNS is at 192.168.1.2, which is on the same subnet as developer (192.168.1.0/24). So pinging DNS works. For the API, it might be on a different subnet, requiring the default gateway. So the developer should verify the default gateway. Option: Check default gateway routing. Distractors: Restart NIC, renew DHCP lease, check firewall. Let's finalize: Correct action: Verify the default gateway is correctly set and can route to the API's subnet.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable the local firewall on the workstation to allow all outbound traffic.
- ✗
Renew the DHCP lease to obtain a new IP address.
- ✗
Restart the network interface card (NIC) to reset the connection.
Why it's wrong here
Restarting the NIC might temporarily reset the connection, but it doesn't address the root cause of routing to the API subnet.
- ✓
Check the default gateway configuration. Ensure it is set to 192.168.1.1 and that the gateway can route traffic to the API's subnet.
Why this is correct
The default gateway is likely missing or misconfigured, preventing traffic to the API subnet. Verifying its setting and reachability resolves the issue.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-901 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this 200-901 question test?
Network Fundamentals — This question tests Network Fundamentals — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check the default gateway configuration. Ensure it is set to 192.168.1.1 and that the gateway can route traffic to the API's subnet. — The issue is that the DNS resolution is likely failing for the internal domain. Since the developer can successfully reach the DNS server, the problem might be a missing DNS record or a misconfigured search domain. However, the correct action is to first verify the DNS resolver configuration, which is already given. Actually, let's re-think: The developer can ping the DNS server but curl times out. The API server is reachable from other devices. The developer's workstation is on the same subnet as the gateway? Actually, the API server is on the same subnet as other devices, but the developer is on a different subnet? The scenario states other devices on the same subnet can reach the API. The developer might have a wrong default gateway. The correct action is to check the default gateway. However, if the default gateway is wrong, pinging the DNS server might still work if it's on the same subnet? But DNS is at 192.168.1.2, which is on the same subnet as developer (192.168.1.0/24). So pinging DNS works. For the API, it might be on a different subnet, requiring the default gateway. So the developer should verify the default gateway. Option: Check default gateway routing. Distractors: Restart NIC, renew DHCP lease, check firewall. Let's finalize: Correct action: Verify the default gateway is correctly set and can route to the API's subnet.
What should I do if I get this 200-901 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-901 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 24, 2026
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