N10-009 Network Troubleshooting Practice Question
A user reports that they cannot access any network resources. The technician runs 'ipconfig' on the workstation and sees that the IP address is 169.254.23.45 with a subnet mask of 255.255.0.0. What is the most likely cause of this issue?
⚠ Common exam trap
Candidates often confuse APIPA with a physical connectivity issue, but APIPA specifically indicates that the DHCP process failed, not necessarily that the cable is unplugged.
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 DHCP server is unreachable or not functioning.
The IP address 169.254.23.45 with a subnet mask of 255.255.0.0 is an Automatic Private IP Addressing (APIPA) address, which is assigned by the operating system when a DHCP discovery attempt fails. This indicates that the workstation was unable to contact a DHCP server to obtain a valid IP configuration, making an unreachable or non-functioning DHCP server the most likely cause.
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's network cable is unplugged.
Why it's wrong here
An unplugged network cable is a Layer 1 physical issue that would prevent any network communication, including DHCP requests. In such a scenario, the network adapter would typically report a 'cable disconnected' status, and `ipconfig` would show no IP address assigned to the interface, or potentially a loopback address, rather than an APIPA address. APIPA requires the physical link to be active to attempt DHCP communication before self-assigning an address.
When this WOULD be correct
A user reports no network access, and ipconfig shows 'Media disconnected' or no IP address. In that case, the most likely cause is a disconnected or faulty network cable.
- ✗
The DNS server is not responding.
Why it's wrong here
DNS server issues primarily affect name resolution, meaning the workstation would struggle to translate domain names into IP addresses. However, a functional DHCP server would still provide the workstation with a valid IP address, subnet mask, and default gateway, allowing for IP-based communication. The presence of an APIPA address explicitly points to a failure in obtaining an IP address from DHCP, not a subsequent name resolution problem.
When this WOULD be correct
A user reports they can access network resources by IP address but not by hostname. The technician checks the workstation's IP configuration and finds a valid IP address. In this scenario, a non-responsive DNS server is the most likely cause.
- ✓
The DHCP server is unreachable or not functioning.
Why this is correct
When a DHCP client fails to receive an IP address lease from a DHCP server after multiple attempts, it automatically assigns itself an APIPA address. This self-configuration occurs within the 169.254.0.0/16 range, indicating that the DHCP server is either offline, unreachable due to network connectivity issues, or misconfigured. The presence of an APIPA address is a strong diagnostic indicator of a DHCP service failure, as the client cannot obtain a valid, routable IP address.
- ✗
The workstation has been assigned a static IP address in the wrong subnet.
Why it's wrong here
If a workstation were configured with a static IP address, it would retain that specific address regardless of DHCP server availability. An APIPA address is a dynamic, automatic fallback mechanism that only occurs when a client is configured for DHCP and fails to obtain a lease from a DHCP server. Therefore, a manually assigned static IP, even if incorrect or in the wrong subnet, would preclude the automatic assignment of an APIPA address.
When this WOULD be correct
This option would be correct in a scenario where a user cannot access network resources, and the workstation has a static IP address that is not in the correct subnet for the network (e.g., 192.168.1.10 with subnet mask 255.255.255.0 on a 10.0.0.0/8 network). The question would explicitly state that the IP is static and not an APIPA address.
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓The DHCP server is unreachable or not functioning.Correct answer▾
Why this is correct
When a DHCP client fails to receive an IP address lease from a DHCP server after multiple attempts, it automatically assigns itself an APIPA address. This self-configuration occurs within the 169.254.0.0/16 range, indicating that the DHCP server is either offline, unreachable due to network connectivity issues, or misconfigured. The presence of an APIPA address is a strong diagnostic indicator of a DHCP service failure, as the client cannot obtain a valid, routable IP address.
✗The workstation's network cable is unplugged.Wrong answer — click to see why▾
Why this is wrong here
An unplugged network cable would result in no IP address or a disconnected status, not an Automatic Private IP Addressing (APIPA) address like 169.254.23.45. APIPA addresses are assigned when DHCP fails, but the link is still active.
★ When this WOULD be the correct answer
A user reports no network access, and ipconfig shows 'Media disconnected' or no IP address. In that case, the most likely cause is a disconnected or faulty network cable.
Why candidates choose this
Candidates may associate any network issue with physical connectivity problems, overlooking that APIPA addresses specifically indicate DHCP failure rather than a complete loss of link.
✗The DNS server is not responding.Wrong answer — click to see why▾
Why this is wrong here
The IP address 169.254.23.45 is an Automatic Private IP Addressing (APIPA) address, which indicates that the workstation failed to obtain an IP from a DHCP server. DNS issues do not cause APIPA addresses; they would result in name resolution failures but the workstation would still have a valid IP.
★ When this WOULD be the correct answer
A user reports they can access network resources by IP address but not by hostname. The technician checks the workstation's IP configuration and finds a valid IP address. In this scenario, a non-responsive DNS server is the most likely cause.
Why candidates choose this
Candidates may confuse DHCP and DNS as both are critical network services, and they might think that a DNS failure could prevent all network access, not just name resolution.
✗The workstation has been assigned a static IP address in the wrong subnet.Wrong answer — click to see why▾
Why this is wrong here
A static IP in the wrong subnet would typically result in a different IP address (not an APIPA 169.254.x.x address) and would not cause the workstation to self-assign an APIPA address. The 169.254.23.45 address indicates DHCP failure, not a static misconfiguration.
★ When this WOULD be the correct answer
This option would be correct in a scenario where a user cannot access network resources, and the workstation has a static IP address that is not in the correct subnet for the network (e.g., 192.168.1.10 with subnet mask 255.255.255.0 on a 10.0.0.0/8 network). The question would explicitly state that the IP is static and not an APIPA address.
Why candidates choose this
Candidates may confuse a static IP in the wrong subnet with an APIPA address, as both can cause connectivity issues. They might think any incorrect IP configuration leads to the same symptom, overlooking the specific 169.254.x.x pattern that uniquely identifies DHCP failure.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
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Related to this question
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Troubleshoot: Network Connectivity
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
Key term
Automatic Private Internet Protocol Addressing
A fallback method used by a device to automatically assign itself an IP address when it cannot obtain one from a DHCP server.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 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 N10-009 exam.