- A
The priority queue has a default policer that drops traffic exceeding a certain rate
Correct because on ASR routers, the priority command includes an implicit policer to prevent starvation of other queues; exceeding this policer causes drops.
- B
The interface bandwidth is set too low, causing the priority queue to be under-provisioned
Why wrong: Incorrect because the priority queue is not bandwidth-constrained; the policer is independent of interface bandwidth.
- C
The class map is not matching the voice traffic correctly
Why wrong: Incorrect because if the class map did not match, the traffic would not enter the priority queue at all.
- D
The router is using WRED on the priority queue
Why wrong: Incorrect because WRED is not applied to priority queues; it is used for non-priority queues to manage congestion.
Quick Answer
The answer is that the priority queue has a default policer that drops voice traffic exceeding a certain rate. This is because on Cisco ASR 1000 series routers, the priority command in a QoS policy map automatically enables a hardware-based policer that limits the bandwidth for priority traffic, typically to a default value like 75% of the interface bandwidth. Even when the priority queue itself is not congested, if the voice traffic rate surpasses this policer, the router drops the excess packets and logs the "priority queue overflow" message. On the ENCOR 350-401 exam, this tests your understanding that priority queuing is not simply a strict priority queue; it includes an implicit policer to prevent starvation of other queues. A common trap is assuming drops only happen when the queue is full, but the policer acts independently. Remember the memory tip: "Priority is policed, not just queued"—the default policer is the silent drop culprit.
350-401 QoS Practice Question
This 350-401 practice question tests your understanding of qos. 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.
An engineer is troubleshooting QoS on a Cisco ASR 1002 router. The router is configured with a policy map that includes a class for voice with a priority command. During congestion, the engineer notices that voice traffic is being dropped even though the priority queue is not congested. The router logs show 'QoS: priority queue overflow'. 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 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 priority queue has a default policer that drops traffic exceeding a certain rate
The correct answer is that the priority queue has a default policer that limits the amount of traffic that can be sent as priority. When the voice traffic exceeds this policer, it is dropped, even if the queue is not full.
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 priority queue has a default policer that drops traffic exceeding a certain rate
Why this is correct
Correct because on ASR routers, the priority command includes an implicit policer to prevent starvation of other queues; exceeding this policer causes drops.
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 interface bandwidth is set too low, causing the priority queue to be under-provisioned
Why it's wrong here
Incorrect because the priority queue is not bandwidth-constrained; the policer is independent of interface bandwidth.
- ✗
The class map is not matching the voice traffic correctly
Why it's wrong here
Incorrect because if the class map did not match, the traffic would not enter the priority queue at all.
- ✗
The router is using WRED on the priority queue
Why it's wrong here
Incorrect because WRED is not applied to priority queues; it is used for non-priority queues to manage congestion.
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.
- →
QoS — study guide chapter
Learn the concepts, then practise the questions
- →
QoS practice questions
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FAQ
Questions learners often ask
What does this 350-401 question test?
QoS — This question tests QoS — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The priority queue has a default policer that drops traffic exceeding a certain rate — The correct answer is that the priority queue has a default policer that limits the amount of traffic that can be sent as priority. When the voice traffic exceeds this policer, it is dropped, even if the queue is not full.
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
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 →
Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer is troubleshooting QoS on a Cisco Nexus 9000 switch. The switch is configured with a policy map that uses a class-default with a bandwidth remaining percent of 100. However, during congestion, traffic in a priority queue (class-map for EF) is experiencing drops even though the priority queue is not fully utilized. What is the most likely cause?
hard- ✓ A.The priority queue is implicitly policed to a default rate on Nexus switches
- B.The class-default bandwidth remaining percent should be set to 0
- C.The priority queue is not configured with a queue-limit
- D.The switch is using strict priority queuing without any shaping
Why A: The correct answer is that the priority queue is policed by default on Nexus switches to prevent starvation of other queues. The priority queue has a policer that drops traffic if it exceeds a certain rate, even if the queue is not congested.
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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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