N10-009 Network Troubleshooting Practice Question
A user reports that they cannot access the internet. The technician is able to ping the default gateway successfully but unable to ping a public IP address (e.g., 8.8.8.8). Which of the following is the most likely cause?
⚠ Common exam trap
It's easy for candidates to confuse DNS resolution with IP connectivity and incorrectly choose 'Incorrect DNS server configuration' when the question explicitly states a public IP address is being pinged, not a hostname.
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 router's default route is missing or misconfigured
Successful ping to the default gateway confirms Layer 2 and Layer 3 connectivity within the local subnet, but failure to ping a public IP like 8.8.8.8 indicates that traffic cannot leave the local network. This is most commonly caused by a missing or misconfigured default route on the router, which prevents the router from forwarding packets destined for external networks to the next-hop ISP gateway.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Incorrect DNS server configuration
Why it's wrong here
An incorrect DNS server configuration primarily affects name resolution, meaning users would be unable to access websites or services using their domain names. However, if the issue were solely DNS, the technician would still be able to ping external IP addresses (e.g., 8.8.8.8) directly. The inability to access the internet, even by IP address (implied by the general statement of no internet access), suggests a broader connectivity problem beyond just name resolution, making DNS an unlikely primary cause.
When this WOULD be correct
In a scenario where a user reports 'cannot access the internet' and the technician can ping 8.8.8.8 but cannot browse by name (e.g., www.google.com), incorrect DNS server configuration would be the likely cause.
- ✓
The router's default route is missing or misconfigured
Why this is correct
The router's default route (0.0.0.0/0) is crucial for forwarding packets to destinations not explicitly listed in its routing table, which typically includes the entire internet. If this route is missing or misconfigured on the router, traffic destined for external networks will be dropped because the router has no instruction on where to send it. The ability to ping the gateway confirms local network connectivity, but the lack of internet access points directly to the router's inability to forward traffic beyond the local subnet.
- ✗
Duplicate IP address on the network
Why it's wrong here
A duplicate IP address on the network would typically cause intermittent and unreliable connectivity due to Address Resolution Protocol (ARP) conflicts and packet misdirection. While this could certainly prevent internet access, the ability to consistently ping the default gateway suggests stable local network communication. If an IP conflict were present, even pinging the gateway would likely be erratic or fail entirely, as the workstation's ARP cache might be poisoned or its packets misdirected.
When this WOULD be correct
A user reports intermittent connectivity and IP conflicts. The technician finds two devices with the same IP via ARP table. The correct answer would be 'Duplicate IP address on the network'.
- ✗
Faulty network interface card
Why it's wrong here
A faulty network interface card (NIC) would prevent the workstation from establishing any network connectivity whatsoever, including communication with the default gateway. The successful ping to the gateway indicates that the NIC is functioning correctly at a basic level, allowing the device to send and receive packets on the local segment. If the NIC were truly faulty, the user would likely experience no network access at all, not just an inability to reach the internet.
When this WOULD be correct
A user cannot access any network resources, and the technician cannot ping the default gateway or any other device. The NIC driver shows errors in Device Manager.
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 router's default route is missing or misconfiguredCorrect answer▾
Why this is correct
The router's default route (0.0.0.0/0) is crucial for forwarding packets to destinations not explicitly listed in its routing table, which typically includes the entire internet. If this route is missing or misconfigured on the router, traffic destined for external networks will be dropped because the router has no instruction on where to send it. The ability to ping the gateway confirms local network connectivity, but the lack of internet access points directly to the router's inability to forward traffic beyond the local subnet.
✗Incorrect DNS server configurationWrong answer — click to see why▾
Why this is wrong here
The user can ping the default gateway but not a public IP like 8.8.8.8, indicating IP routing works locally but fails beyond the local network. DNS is not involved because the test uses an IP address, not a hostname.
★ When this WOULD be the correct answer
In a scenario where a user reports 'cannot access the internet' and the technician can ping 8.8.8.8 but cannot browse by name (e.g., www.google.com), incorrect DNS server configuration would be the likely cause.
Why candidates choose this
Candidates often associate internet access problems with DNS, but the question explicitly tests with a public IP address, bypassing DNS. They may overlook that DNS is only needed for name resolution, not IP connectivity.
✗Duplicate IP address on the networkWrong answer — click to see why▾
Why this is wrong here
The user can ping the default gateway but not a public IP, indicating layer 3 routing failure. A duplicate IP address would cause intermittent connectivity or inability to ping the gateway, not a specific failure to reach external IPs.
★ When this WOULD be the correct answer
A user reports intermittent connectivity and IP conflicts. The technician finds two devices with the same IP via ARP table. The correct answer would be 'Duplicate IP address on the network'.
Why candidates choose this
Candidates may confuse symptoms of DNS failure (which affects name resolution, not IP pings) with IP conflicts, or assume any connectivity issue could be caused by duplicate addresses.
✗Faulty network interface cardWrong answer — click to see why▾
Why this is wrong here
A faulty NIC would prevent successful pings to the default gateway, but the technician can ping the gateway, indicating the NIC is working.
★ When this WOULD be the correct answer
A user cannot access any network resources, and the technician cannot ping the default gateway or any other device. The NIC driver shows errors in Device Manager.
Why candidates choose this
Candidates may associate internet access issues with hardware failure, overlooking that successful gateway pings rule out a faulty NIC.
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
Go deeper
Related to this question
Learn chapter
Troubleshoot: Cable and Physical Layer
Key term
Public IP address
A globally unique IP address assigned to a device that allows it to communicate directly over the internet.
Key term
ICMP
ICMP is a network-layer protocol used by network devices to send error messages and operational information about network connectivity.
About these practice questions
This N10-009 question is part of Courseiva's 464-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.