N10-009 Network Troubleshooting Practice Question
A network technician is troubleshooting a workstation that is experiencing intermittent connectivity and slow file transfers. The technician has confirmed that the patch cable passes a cable tester, the switch port is not error-disabled, and the workstation's NIC is configured for autonegotiation. The switch port is also set to autonegotiate. Which of the following should the technician check next?
⚠ Common exam trap
The N10-009 exam often tests the misconception that if a cable tester passes and autonegotiation is enabled on both ends, the link must be fully functional, but the trap is that autonegotiation can fail silently, resulting in a duplex mismatch that causes the exact symptoms described.
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 duplex and speed settings on both ends
Intermittent connectivity and slow file transfers, despite a passing cable test and autonegotiation on both ends, strongly indicate a duplex mismatch. When both sides are set to autonegotiate but one side fails to negotiate correctly (e.g., due to a faulty NIC or switch port), they may fall back to half-duplex while the other remains full-duplex, causing collisions, CRC errors, and retransmissions. The technician should verify the actual negotiated duplex and speed on both the workstation NIC and the switch port using commands like 'show interfaces' or NIC driver properties.
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 route table on the default gateway
Why it's wrong here
The route table on a default gateway primarily dictates how network traffic destined for remote networks, outside the local subnet, is forwarded. If a workstation is experiencing intermittent performance or slow file transfers, especially within its local network segment, issues with routing tables are unlikely to be the cause. Routing problems typically manifest as an inability to reach specific external destinations or the internet, not as general slowness or intermittent connectivity for local resources.
When this WOULD be correct
A workstation can reach local resources but not remote networks, and other devices on the same subnet have no issues. The technician should check the route table on the default gateway for missing or incorrect routes.
- ✓
The duplex and speed settings on both ends
Why this is correct
A duplex mismatch occurs when one network device operates in half-duplex mode while the connected device operates in full-duplex mode, often due to autonegotiation failures or manual misconfiguration. This scenario leads to severe performance degradation because the full-duplex device transmits without listening for collisions, while the half-duplex device expects to detect collisions and retransmit. The result is excessive frame loss, retransmissions, and a drastic reduction in effective throughput, manifesting as intermittent connectivity and extremely slow file transfers.
- ✗
The DNS server configuration
Why it's wrong here
DNS (Domain Name System) server configuration is critical for resolving human-readable hostnames into numerical IP addresses. While a misconfigured DNS server would prevent a workstation from accessing resources by name, it would not cause intermittent connectivity or slow performance for established connections or file transfers that rely on direct IP communication. Once an IP address is resolved, subsequent data transfer operations do not repeatedly query DNS, making it an unlikely cause for ongoing performance degradation.
When this WOULD be correct
A user reports that they can access internal resources by IP address but not by hostname, and external websites fail to load. The technician should check DNS server configuration to resolve name resolution failures.
- ✗
The MAC address filtering on the switch
Why it's wrong here
MAC address filtering, typically implemented on network switches or wireless access points, is a security mechanism that permits or denies network access based on a device's unique hardware address. If MAC filtering were enabled and the workstation's MAC address was not permitted, the device would be completely unable to connect to the network at all. It would not result in intermittent connectivity or slow data transfers once a connection is established, making it an unsuitable explanation for the described symptoms.
When this WOULD be correct
A technician is troubleshooting a workstation that cannot connect to the network at all, but other devices on the same switch work fine. The switch logs show 'MAC address violation' errors, and the workstation's MAC is not on the allowed list.
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 duplex and speed settings on both endsCorrect answer▾
Why this is correct
A duplex mismatch occurs when one network device operates in half-duplex mode while the connected device operates in full-duplex mode, often due to autonegotiation failures or manual misconfiguration. This scenario leads to severe performance degradation because the full-duplex device transmits without listening for collisions, while the half-duplex device expects to detect collisions and retransmit. The result is excessive frame loss, retransmissions, and a drastic reduction in effective throughput, manifesting as intermittent connectivity and extremely slow file transfers.
✗The route table on the default gatewayWrong answer — click to see why▾
Why this is wrong here
The route table on the default gateway affects routing between subnets, not intermittent connectivity or slow file transfers on a local switch port. The issue is likely at Layer 2 (duplex/speed mismatch), not Layer 3 routing.
★ When this WOULD be the correct answer
A workstation can reach local resources but not remote networks, and other devices on the same subnet have no issues. The technician should check the route table on the default gateway for missing or incorrect routes.
Why candidates choose this
Candidates may think any connectivity issue involves routing, especially when 'intermittent' suggests path problems, but the symptoms (slow transfers, autonegotiation) point to duplex mismatch instead.
✗The DNS server configurationWrong answer — click to see why▾
Why this is wrong here
Intermittent connectivity and slow file transfers with a confirmed good cable and autonegotiation on both ends point to duplex mismatch or speed negotiation issues, not DNS. DNS affects name resolution, not throughput or link stability.
★ When this WOULD be the correct answer
A user reports that they can access internal resources by IP address but not by hostname, and external websites fail to load. The technician should check DNS server configuration to resolve name resolution failures.
Why candidates choose this
Candidates often associate any connectivity or performance issue with DNS because DNS is a common troubleshooting step, but the symptoms here (intermittent connectivity and slow transfers) are classic for layer 1/2 issues, not DNS.
✗The MAC address filtering on the switchWrong answer — click to see why▾
Why this is wrong here
The question describes intermittent connectivity and slow file transfers with confirmed cable integrity and autonegotiation settings, pointing to a duplex mismatch issue. MAC address filtering would cause complete connectivity failure for unauthorized devices, not intermittent issues or slow transfers.
★ When this WOULD be the correct answer
A technician is troubleshooting a workstation that cannot connect to the network at all, but other devices on the same switch work fine. The switch logs show 'MAC address violation' errors, and the workstation's MAC is not on the allowed list.
Why candidates choose this
Candidates may confuse MAC filtering as a common cause of connectivity problems, especially when they recall security features on switches, but they overlook that it typically results in total lack of access rather than intermittent performance issues.
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?”
Go deeper
Related to this question
Learn chapter
Troubleshooting Methodology
Key term
NIC
A NIC is a hardware component that connects a computer to a network, enabling communication over wired or wireless media.
Key term
Cyclic Redundancy Check
A Cyclic Redundancy Check (CRC) is an error-detecting code used to verify that data transmitted over a network or stored on a device has not been corrupted.
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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.