The answer is that the DNS A record for www.example.com is incorrect and must be updated to point to 192.0.2.10. The nslookup output reveals the domain resolves to 192.0.2.20, while the actual web server lives at 192.0.2.10, so the mismatch directly explains why internal hosts can ping the server by IP but fail to reach it via the FQDN. This scenario tests your understanding of DNS resolution versus IP connectivity—a classic CCNA 200-301 v2 troubleshooting trap where the DNS server is reachable and responds, but the A record data itself is wrong. The key distinction is that pinging the IP works (proving Layer 3 reachability), while nslookup bypasses the host’s cache and still returns the wrong address, ruling out cache or firewall issues. For the exam, remember the memory tip: “A record, A correct IP”—if the ping works but the name fails, the problem is almost always the A record pointing to the wrong address.
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.
Exhibit
C:\Users\admin> nslookup www.example.com
Server: dns.example.com
Address: 192.0.2.5
Name: www.example.com
Address: 198.51.100.1
C:\Users\admin> ping 198.51.100.1
Pinging 198.51.100.1 with 32 bytes of data:
Reply from 192.0.2.10: Destination host unreachable.
C:\Users\admin> ping 192.0.2.10
Pinging 192.0.2.10 with 32 bytes of data:
Reply from 192.0.2.10: bytes=32 time<1ms TTL=128
A network administrator is troubleshooting an issue where internal hosts can ping the company's web server by IP address (192.0.2.10) but cannot access it using the fully qualified domain name www.example.com. The DNS server (192.0.2.5) is reachable and responds to queries. The administrator runs nslookup www.example.com from a host and receives the following output:
C:\> nslookup www.example.com
Server: UnKnown
Address: 192.0.2.5
Name: www.example.com
Address: 192.0.2.20
Based on the output, what is the most likely cause of the 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.
C:\Users\admin> nslookup www.example.com
Server: dns.example.com
Address: 192.0.2.5
Name: www.example.com
Address: 198.51.100.1
C:\Users\admin> ping 198.51.100.1
Pinging 198.51.100.1 with 32 bytes of data:
Reply from 192.0.2.10: Destination host unreachable.
C:\Users\admin> ping 192.0.2.10
Pinging 192.0.2.10 with 32 bytes of data:
Reply from 192.0.2.10: bytes=32 time<1ms TTL=128
A
The host's DNS cache is corrupted; flush it using ipconfig /flushdns.
Why wrong: Flushing DNS cache clears local entries, but the nslookup response shows the DNS server itself is returning the wrong address, not the local cache.
B
The DNS A record for www.example.com is incorrect; update it to point to 192.0.2.10.
The nslookup shows the DNS server returns 198.51.100.1, but the actual server is at 192.0.2.10. Correcting the A record resolves the mismatch.
C
The web server's firewall is blocking traffic from the host; add an allow rule.
Why wrong: The host can ping 192.0.2.10 successfully, indicating no firewall blocking ICMP. The issue is name resolution, not firewall rules.
D
The DNS server is not authoritative for the example.com zone; delegate the zone to a different server.
Why wrong: The nslookup response includes the server name dns.example.com, confirming it is authoritative for the zone. Delegation is not needed.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The DNS A record for www.example.com is incorrect; update it to point to 192.0.2.10.
The nslookup output shows that www.example.com resolves to 192.0.2.20, but the web server is at 192.0.2.10. This indicates the DNS A record is incorrect and must be updated to point to the correct IP. Pinging by IP works because it bypasses DNS, confirming network connectivity. The host's DNS cache is not the issue because nslookup queries the server directly and still returns the wrong address. The firewall is not involved since pinging by IP succeeds, and the DNS server is authoritative (the response is received).
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 host's DNS cache is corrupted; flush it using ipconfig /flushdns.
Why it's wrong here
Flushing DNS cache clears local entries, but the nslookup response shows the DNS server itself is returning the wrong address, not the local cache.
✓
The DNS A record for www.example.com is incorrect; update it to point to 192.0.2.10.
Why this is correct
The nslookup shows the DNS server returns 198.51.100.1, but the actual server is at 192.0.2.10. Correcting the A record resolves the mismatch.
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.
✗
The web server's firewall is blocking traffic from the host; add an allow rule.
Why it's wrong here
The host can ping 192.0.2.10 successfully, indicating no firewall blocking ICMP. The issue is name resolution, not firewall rules.
✗
The DNS server is not authoritative for the example.com zone; delegate the zone to a different server.
Why it's wrong here
The nslookup response includes the server name dns.example.com, confirming it is authoritative for the zone. Delegation is not needed.
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 DNS A record for www.example.com is incorrect; update it to point to 192.0.2.10.Correct answer▾
Why this is correct
The nslookup shows the DNS server returns 198.51.100.1, but the actual server is at 192.0.2.10. Correcting the A record resolves the mismatch.
✗The host's DNS cache is corrupted; flush it using ipconfig /flushdns.Wrong answer — click to see why▾
Why this is wrong here
The nslookup output shows the DNS server is returning an incorrect IP address (198.51.100.1) for www.example.com, not a local cache issue. Flushing the DNS cache would not resolve the problem because the host is querying the DNS server and receiving the wrong answer.
Why candidates choose this
Students often confuse DNS resolution failures with local cache corruption, especially when the host can ping the correct IP but not the FQDN. The ipconfig /flushdns command is a common troubleshooting step for DNS issues, but it is only effective when the cache contains stale or incorrect entries, not when the authoritative server returns a wrong record.
✗The web server's firewall is blocking traffic from the host; add an allow rule.Wrong answer — click to see why▾
Why this is wrong here
The host can successfully ping the web server at 192.0.2.10, which indicates that ICMP traffic is not blocked by the firewall. The problem is that the host is trying to reach the wrong IP address (198.51.100.1) due to DNS resolution, not that the correct IP is being blocked.
Why candidates choose this
Firewall rules are a common cause of connectivity issues, and students may assume that if a web server is unreachable by name, the firewall is blocking HTTP/HTTPS traffic. However, the successful ping to the correct IP shows that the network path is open; the issue is purely with name resolution.
✗The DNS server is not authoritative for the example.com zone; delegate the zone to a different server.Wrong answer — click to see why▾
Why this is wrong here
The nslookup response includes the server name 'dns.example.com', which indicates that the DNS server is authoritative for the example.com zone. If it were not authoritative, the response would typically show a non-authoritative answer or refer to another server. Delegation is not needed because the server is already authoritative.
Why candidates choose this
Students may think that if a DNS server returns an incorrect IP, it might not be authoritative for the zone. However, the nslookup output clearly shows the server is authoritative. The issue is a misconfiguration within the zone, not a lack of authority.
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
The trap here is that candidates may assume a DNS server that responds to queries is functioning correctly, overlooking that the response itself can contain an incorrect A record, which is the actual cause of the resolution failure.
Trap categories for this question
Command / output trap
Flushing DNS cache clears local entries, but the nslookup response shows the DNS server itself is returning the wrong address, not the local cache.
Detailed technical explanation
How to think about this question
DNS A records map a hostname to an IPv4 address; if the record points to a wrong IP (e.g., 192.0.2.99 instead of 192.0.2.10), the host will attempt to connect to the wrong destination, causing the FQDN access failure while IP-based access works. The nslookup command queries the DNS server directly, bypassing the local cache, so its output reveals the actual record value. In real-world scenarios, this often occurs after a server migration where the DNS record is not updated promptly.
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 practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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 DNS A record for www.example.com is incorrect; update it to point to 192.0.2.10. — The nslookup output shows that www.example.com resolves to 192.0.2.20, but the web server is at 192.0.2.10. This indicates the DNS A record is incorrect and must be updated to point to the correct IP. Pinging by IP works because it bypasses DNS, confirming network connectivity. The host's DNS cache is not the issue because nslookup queries the server directly and still returns the wrong address. The firewall is not involved since pinging by IP succeeds, and the DNS server is authoritative (the response is received).
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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