- A
The IP SLA DNS probe is using a cached DNS response from the router's DNS resolver, so it does not actually query the server.
Correct. If the router has DNS caching enabled, the IP SLA DNS probe may receive a cached response, making it appear as if the server is reachable when it is not.
- B
The IP SLA DNS probe must be configured with a 'timeout' value lower than 50 ms to detect the failure.
Why wrong: Incorrect because the RTT is 50 ms, so a timeout lower than that would cause a false failure; the issue is that the probe is getting a response from a cache.
- C
The DNS server is responding to the probe but not to other queries because the probe uses a different port.
Why wrong: Incorrect because DNS uses UDP port 53 by default; the probe uses the same port as regular queries.
- D
The IP SLA operation is configured with a 'frequency' that is too low, causing the probe to be sent before the server times out.
Why wrong: Incorrect because frequency does not affect whether the probe receives a response; it only controls how often probes are sent.
Quick Answer
The answer is that the IP SLA DNS probe shows active despite the server being down because it is using a cached DNS response from the router’s local DNS resolver rather than sending a fresh query to the target server. This is the most likely reason for a false positive due to caching, as the router’s DNS cache retains the previous successful resolution for 'example.com' and serves it to the IP SLA operation, which then reports a successful round-trip time even though the actual DNS server at 10.1.1.1 is unresponsive. On the ENCOR 350-401 exam, this scenario tests your understanding of how IP SLA probes interact with local caching mechanisms and the importance of verifying that the probe bypasses cached data when monitoring server health. A common trap is assuming that a successful RTT always confirms end-to-end connectivity, but the router’s resolver may answer from cache without ever reaching the server. Memory tip: “Cache can fake the state” — if the RTT is suspiciously low or consistent, suspect a cached reply.
350-401 IP SLA Practice Question
This 350-401 practice question tests your understanding of ip sla. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 network engineer configures IP SLA 20 to monitor the response time of a DNS server at 10.1.1.1 using DNS query for 'example.com'. The operation is used to influence routing decisions. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 50 ms', but the DNS server is actually down and not responding to any queries. What is the most likely reason?
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 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 IP SLA DNS probe is using a cached DNS response from the router's DNS resolver, so it does not actually query the server.
The DNS probe may be receiving a response from a cache (either on the router itself or an intermediate DNS cache) rather than the actual DNS server. This can cause the probe to succeed even if the server is down.
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 IP SLA DNS probe is using a cached DNS response from the router's DNS resolver, so it does not actually query the server.
Why this is correct
Correct. If the router has DNS caching enabled, the IP SLA DNS probe may receive a cached response, making it appear as if the server is reachable when it is not.
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 IP SLA DNS probe must be configured with a 'timeout' value lower than 50 ms to detect the failure.
Why it's wrong here
Incorrect because the RTT is 50 ms, so a timeout lower than that would cause a false failure; the issue is that the probe is getting a response from a cache.
- ✗
The DNS server is responding to the probe but not to other queries because the probe uses a different port.
- ✗
The IP SLA operation is configured with a 'frequency' that is too low, causing the probe to be sent before the server times out.
Why it's wrong here
Incorrect because frequency does not affect whether the probe receives a response; it only controls how often probes are sent.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 350-401 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.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this 350-401 question test?
IP SLA — This question tests IP SLA — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The IP SLA DNS probe is using a cached DNS response from the router's DNS resolver, so it does not actually query the server. — The DNS probe may be receiving a response from a cache (either on the router itself or an intermediate DNS cache) rather than the actual DNS server. This can cause the probe to succeed even if the server is down.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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
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Last reviewed: Jun 18, 2026
This 350-401 practice question is part of Courseiva's free Cisco 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 350-401 exam.
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