- A
Ping
Why wrong: Ping can test connectivity but does not directly diagnose DNS resolution issues.
- B
ipconfig /flushdns
Why wrong: Flushing the DNS cache may help if the cache is corrupted, but it does not test DNS server functionality.
- C
nslookup
nslookup queries the configured DNS server to resolve a hostname, allowing the technician to see if DNS is working.
- D
Netstat
Why wrong: Netstat shows active connections and listening ports, not DNS resolution details.
Question 36 of 1,020
How to Use nslookup to Verify DNS Server Responses
This 220-1201 practice question tests your understanding of networking tools. 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 technician is troubleshooting a user's computer that can reach internal servers by IP address but not by hostname. Other computers on the same subnet work correctly. Which tool should the technician use to check the computer's DNS resolution?
Quick Answer
The answer is nslookup, the command-line tool used to query DNS servers and verify hostname-to-IP resolution. When a user can reach internal servers by IP address but not by hostname, while other computers on the same subnet work correctly, the problem is almost certainly DNS-related rather than a network connectivity issue. The nslookup command for DNS resolution directly tests whether the computer’s configured DNS server is responding and returning the correct records, isolating the fault to the DNS client or server configuration. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of basic network troubleshooting—a common trap is to reach for ping or ipconfig first, but those tools won’t reveal a misconfigured or unresponsive DNS server. Remember the memory tip: “Names fail? nslookup to the rescue.”
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
✓
nslookup
The user's computer can reach internal servers by IP address but not by hostname, and other computers on the same subnet work correctly. This isolates the problem to the local DNS resolution on the affected machine. The `nslookup` tool is specifically designed to query DNS servers and verify whether a hostname resolves to the correct IP address, making it the appropriate tool to diagnose the DNS resolution failure.
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.
- ✗
Ping
Why it's wrong here
Ping can test connectivity but does not directly diagnose DNS resolution issues.
- ✗
ipconfig /flushdns
Why it's wrong here
Flushing the DNS cache may help if the cache is corrupted, but it does not test DNS server functionality.
- ✓
nslookup
Why this is correct
nslookup queries the configured DNS server to resolve a hostname, allowing the technician to see if DNS is working.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Netstat
Why it's wrong here
Netstat shows active connections and listening ports, not DNS resolution details.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose `ipconfig /flushdns` (Option B) thinking it will fix the problem, but the question asks for a tool to *check* DNS resolution, not to clear the cache; `nslookup` is the correct diagnostic command.
Trap categories for this question
Command / output trap
Netstat shows active connections and listening ports, not DNS resolution details.
Detailed technical explanation
How to think about this question
`nslookup` sends DNS queries to the configured DNS server using the DNS protocol (RFC 1035) and returns the resolved IP address or an error message such as 'Non-existent domain' or 'server failed.' This tool can also be used to query specific record types (e.g., A, AAAA, MX) and to test against alternative DNS servers, which helps isolate whether the issue lies with the client's DNS configuration or the server itself. In real-world scenarios, a misconfigured hosts file or a corrupted DNS client service can cause resolution failures that `nslookup` can pinpoint.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Networking Tools — This question tests Networking Tools — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: nslookup — The user's computer can reach internal servers by IP address but not by hostname, and other computers on the same subnet work correctly. This isolates the problem to the local DNS resolution on the affected machine. The `nslookup` tool is specifically designed to query DNS servers and verify whether a hostname resolves to the correct IP address, making it the appropriate tool to diagnose the DNS resolution failure.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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