N10-009 Network Troubleshooting Practice Question
A user's workstation shows an IP address of 169.254.15.7 with a subnet mask of 255.255.0.0. The user cannot access any network resources. Which of the following is the most likely cause?
⚠ Common exam trap
Test-takers frequently confuse APIPA with a DNS or gateway issue, but APIPA specifically indicates DHCP failure, not a problem with higher-layer services or routing.
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
The IP address 169.254.15.7 with a /16 subnet mask is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when a DHCP client fails to obtain a lease. This indicates the workstation cannot reach a DHCP server, so the most likely cause is that the DHCP server is unreachable.
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 DNS server is not responding
Why it's wrong here
The Domain Name System (DNS) server is responsible for resolving hostnames to IP addresses, a function that occurs after a workstation has successfully obtained its network configuration. While DHCP typically provides the DNS server addresses, a non-responsive DNS server would not prevent the workstation from acquiring an IP address, subnet mask, and default gateway from the DHCP server. The DHCP process completes independently of DNS server responsiveness.
When this WOULD be correct
In a scenario where a workstation has a valid static IP address but cannot resolve hostnames, and other network connectivity (e.g., ping to IP addresses) works, then a non-responsive DNS server would be the most likely cause.
- ✓
The DHCP server is unreachable
Why this is correct
The IP address 169.254.15.7 is an Automatic Private IP Addressing (APIPA) address. This range (169.254.0.0/16) is automatically assigned by a client when it is configured to obtain an IP address via DHCP but fails to locate or communicate with a DHCP server on the network. Therefore, the workstation cannot obtain a valid IP configuration from the network's DHCP service, leading to this self-assigned address.
- ✗
The subnet mask is incorrect
Why it's wrong here
An incorrect subnet mask would indicate that the workstation successfully received an IP configuration from a DHCP server, but the server itself was misconfigured or provided erroneous information. The presence of an APIPA address, however, explicitly signifies a failure in the DHCP lease acquisition process, meaning no configuration, correct or incorrect, was received from a DHCP server. The issue is a lack of DHCP communication, not a flawed DHCP assignment.
- ✗
The default gateway is down
Why it's wrong here
A default gateway is essential for routing traffic to destinations outside the local subnet, but its operational status does not impact the initial DHCP lease acquisition process. DHCP communication occurs via broadcast messages within the local network segment, which does not require a default gateway to be functional. The workstation would still successfully obtain an IP address, subnet mask, and other parameters from DHCP, even if the gateway were down.
When this WOULD be correct
A workstation has a static IP address (e.g., 192.168.1.10) and can communicate with other devices on the same subnet but cannot access the internet or remote networks. In this scenario, the most likely cause is that the default gateway is down or misconfigured.
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 unreachableCorrect answer▾
Why this is correct
The IP address 169.254.15.7 is an Automatic Private IP Addressing (APIPA) address. This range (169.254.0.0/16) is automatically assigned by a client when it is configured to obtain an IP address via DHCP but fails to locate or communicate with a DHCP server on the network. Therefore, the workstation cannot obtain a valid IP configuration from the network's DHCP service, leading to this self-assigned address.
✗The DNS server is not respondingWrong answer — click to see why▾
Why this is wrong here
The IP address 169.254.15.7 is an Automatic Private IP Addressing (APIPA) address, which indicates that the workstation failed to obtain an IP from a DHCP server. A non-responsive DNS server would not cause the workstation to self-assign an APIPA address; it would still have a valid DHCP-assigned IP.
★ When this WOULD be the correct answer
In a scenario where a workstation has a valid static IP address but cannot resolve hostnames, and other network connectivity (e.g., ping to IP addresses) works, then a non-responsive DNS server would be the most likely cause.
Why candidates choose this
Candidates often associate network resource access issues with DNS problems, overlooking that APIPA addresses are a clear indicator of DHCP failure rather than DNS failure.
✗The default gateway is downWrong answer — click to see why▾
Why this is wrong here
The IP address 169.254.15.7 is an Automatic Private IP Addressing (APIPA) address, which indicates the workstation failed to obtain an IP from a DHCP server. A down default gateway would not cause the workstation to self-assign an APIPA address; instead, the workstation would retain its DHCP-assigned IP but lose connectivity beyond the local subnet.
★ When this WOULD be the correct answer
A workstation has a static IP address (e.g., 192.168.1.10) and can communicate with other devices on the same subnet but cannot access the internet or remote networks. In this scenario, the most likely cause is that the default gateway is down or misconfigured.
Why candidates choose this
Candidates often associate 'cannot access any network resources' with a gateway issue, overlooking that APIPA addresses result from DHCP failure, not gateway problems. The symptom of no connectivity to any resource (including local) should steer them away from a gateway-only cause.
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?”
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Related to this question
Learn chapter
Troubleshoot: Network Connectivity
Key term
DHCP
Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses and network settings to devices on a network, so they can communicate without manual configuration.
Key term
Subnet mask
A subnet mask is a 32-bit number that helps a computer or network device determine which part of an IP address identifies the network and which part identifies the host device on that network.
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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.