CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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.
Clients on a network can browse the internet by IP address but fail when using hostnames. What is the most likely problem?
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
✓
The client is using the wrong DNS server address.
The client can browse by IP address but not by hostname, which indicates that IP connectivity and routing are functional, but name resolution is failing. Since DNS translates hostnames to IP addresses, the most likely fault is that the client is configured with an incorrect DNS server address, preventing it from resolving domain names.
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.
✗
The default gateway on the PC is incorrect.
Why it's wrong here
Internet reachability by IP shows the gateway path works.
When this WOULD be correct
In a different scenario where a question states that clients cannot access any external resources, including IP addresses, and the default gateway is incorrectly configured, this option would be correct. For example, if the question specifies that the clients are unable to communicate outside their local subnet, then an incorrect default gateway would be the cause.
✓
The client is using the wrong DNS server address.
Why this is correct
That is the direct cause of hostname resolution failure here.
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.
✗
NAT overload is failing on the edge router.
Why it's wrong here
NAT is clearly working because the host reaches 8.8.8.8.
When this WOULD be correct
In a scenario where clients cannot access any external resources, including both IP addresses and hostnames, and the question specifies issues with NAT configurations, this option could be correct if the NAT overload configuration is misconfigured or overloaded.
✗
The switchport must be converted to a routed port.
In a different scenario, if the question stated that clients are unable to communicate with devices on different subnets and the switchport configuration was incorrectly set to access mode instead of routed mode, this option would be correct. It would indicate that the switchport needs to be configured to allow routing between VLANs.
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 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The client is using the wrong DNS server address.Correct answer▾
Why this is correct
That is the direct cause of hostname resolution failure here.
✗The default gateway on the PC is incorrect.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because if the default gateway on the PC were incorrect, the client would not be able to reach any external IP addresses, not just hostnames. The issue specifically pertains to DNS resolution, not routing.
★ When this WOULD be the correct answer
In a different scenario where a question states that clients cannot access any external resources, including IP addresses, and the default gateway is incorrectly configured, this option would be correct. For example, if the question specifies that the clients are unable to communicate outside their local subnet, then an incorrect default gateway would be the cause.
Why candidates choose this
Candidates might choose this option because they associate connectivity issues with routing problems, and the default gateway is a common troubleshooting point for network access issues, leading to confusion about the specific nature of the problem.
✗NAT overload is failing on the edge router.Wrong answer — click to see why▾
Why this is wrong here
NAT overload failing on the edge router would typically affect the ability to connect to the internet entirely, not just when using hostnames. Since clients can browse by IP, this indicates NAT is functioning correctly.
★ When this WOULD be the correct answer
In a scenario where clients cannot access any external resources, including both IP addresses and hostnames, and the question specifies issues with NAT configurations, this option could be correct if the NAT overload configuration is misconfigured or overloaded.
Why candidates choose this
Candidates might be drawn to this option due to a misunderstanding of NAT functionality, assuming that any internet connectivity issue must relate to NAT configurations, especially if they have seen similar questions in practice exams.
✗The switchport must be converted to a routed port.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the issue described pertains to DNS resolution, not layer 2 switching or routing. The problem is related to hostname resolution failures, which are not affected by the switchport type.
★ When this WOULD be the correct answer
In a different scenario, if the question stated that clients are unable to communicate with devices on different subnets and the switchport configuration was incorrectly set to access mode instead of routed mode, this option would be correct. It would indicate that the switchport needs to be configured to allow routing between VLANs.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of the network layers, thinking that routing issues at the switchport level could impact hostname resolution, especially if they are familiar with switch configurations.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between IP connectivity issues and name resolution issues, and the trap here is that candidates may incorrectly blame the default gateway or NAT when the symptom clearly isolates the problem to DNS.
Trap categories for this question
Command / output trap
Internet reachability by IP shows the gateway path works.
Detailed technical explanation
How to think about this question
DNS resolution relies on the client sending a query to a configured DNS server (typically UDP port 53). If the DNS server address is wrong or unreachable, the client will fail to resolve hostnames, even though it has full IP connectivity. In a real-world scenario, this often occurs when DHCP provides a stale or incorrect DNS server, or when the client is statically configured with a non-existent DNS server.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Network Services and Security — This question tests Network Services and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The client is using the wrong DNS server address. — The client can browse by IP address but not by hostname, which indicates that IP connectivity and routing are functional, but name resolution is failing. Since DNS translates hostnames to IP addresses, the most likely fault is that the client is configured with an incorrect DNS server address, preventing it from resolving domain names.
What should I do if I get this 200-301 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.
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Question Discussion
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