The answer is an ACL blocking port 80 or 443. This is correct because a successful ping confirms Layer 3 IP connectivity via ICMP, but the inability to open a web page points to a Layer 4 port filtering issue; an access control list can permit ICMP echo requests while denying TCP traffic on ports 80 and 443, which are used for HTTP and HTTPS. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how ACLs operate at different OSI layers—a common trap is assuming a failed web access means a total network outage, when in fact ICMP and TCP are filtered independently. Remember the key distinction: ping uses ICMP, web browsing uses TCP, so an ACL can block one without affecting the other. A useful memory tip is “Ping is ICMP, web is TCP—ACLs filter by port, not by reach.”
N10-009 Network Troubleshooting Practice Question
This N10-009 practice question tests your understanding of network troubleshooting. 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 user reports that they cannot access a web server at 10.0.1.200. The user can ping the server's IP address but cannot open the web page. The web server is known to be running and accessible from other users on the same subnet. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ACL blocking port 80 or 443
The user can ping the server (ICMP works) but cannot access the web page, which indicates Layer 3 connectivity is fine but the specific TCP ports (80 for HTTP or 443 for HTTPS) are being blocked. An ACL applied on the server, a switch, or a router between the user and the server is the most likely cause, as it would permit ICMP echo requests while denying HTTP/HTTPS traffic. Other users on the same subnet can access the server, ruling out server-side or subnet-wide issues.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Default gateway is misconfigured
Why it's wrong here
The default gateway is not needed for same-subnet communication.
✓
ACL blocking port 80 or 443
Why this is correct
ICMP is allowed but TCP traffic to the web server is blocked, which is typical of an ACL filtering specific ports.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
DNS resolution failure
Why it's wrong here
The user is accessing the server by IP address, so DNS is not required.
✗
Duplicate IP address
Why it's wrong here
A duplicate IP would cause intermittent connectivity and likely affect ping as well.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a successful ping means full network connectivity, but ICMP and TCP are separate protocols that can be filtered independently by ACLs, so ping working does not guarantee web access.
Detailed technical explanation
How to think about this question
ACLs can filter traffic based on protocol and port numbers; a common misconfiguration is allowing ICMP (used by ping) while blocking TCP ports 80 and 443. In Cisco IOS, an extended ACL applied inbound on the server's interface might permit icmp any any but deny tcp any any eq 80, which would produce exactly this symptom. Real-world scenarios often involve security teams adding ACLs for web servers without realizing they also need to permit ICMP for troubleshooting.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Troubleshooting — This question tests Network Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ACL blocking port 80 or 443 — The user can ping the server (ICMP works) but cannot access the web page, which indicates Layer 3 connectivity is fine but the specific TCP ports (80 for HTTP or 443 for HTTPS) are being blocked. An ACL applied on the server, a switch, or a router between the user and the server is the most likely cause, as it would permit ICMP echo requests while denying HTTP/HTTPS traffic. Other users on the same subnet can access the server, ruling out server-side or subnet-wide issues.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.