Question 1mediummatching
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Quick Answer
The correct match for Weighted Tail-drop is "Drops packets based on a per-class drop threshold but still drops all when threshold exceeded." This mechanism combines the simplicity of tail-drop with class-based differentiation: each class has its own queue threshold, and once that threshold is reached, all subsequent packets for that class are dropped until the queue recovers. Unlike standard tail-drop, which drops indiscriminately when the single queue is full, Weighted Tail-drop allows higher-priority classes to retain buffer space longer. On the ENCOR 350-401 exam, this topic tests your ability to distinguish between congestion avoidance mechanisms like RED, WRED, and ECN, often in drag-and-drop or scenario-based questions. A common trap is confusing Weighted Tail-drop with WRED—remember that WRED uses probabilistic early dropping based on IP precedence or DSCP, while Weighted Tail-drop is a hard threshold drop per class. Memory tip: "Weighted Tail-drop is a hard stop per class; WRED is a soft warning per class."
350-401 QoS Practice Question
This 350-401 practice question tests your understanding of qos. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Drag and drop each congestion avoidance mechanism on the left to its matching method on the right.
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
✓
Tail-drop: Drops all arriving packets when the queue is full
Tail-drop drops all packets when queue is full; RED starts dropping packets probabilistically before queue full; WRED uses IP precedence or DSCP to vary drop probability per class.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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?
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: Tail-drop: Drops all arriving packets when the queue is full — Tail-drop drops all packets when queue is full; RED starts dropping packets probabilistically before queue full; WRED uses IP precedence or DSCP to vary drop probability per class.
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.
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
2 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. Drag and drop each congestion avoidance mechanism on the left to its method on the right.
medium- ✓ P1.Tail-drop: Drops all packets when queue is full
- ✓ P2.RED: Random early detection based on average queue depth
- ✓ P3.WRED: Weighted random early detection using IP precedence or DSCP
- ✓ P4.Tail-drop (variant): No selective drop before congestion
- ✓ P5.WRED (variant): Drops packets with lower priority more aggressively
Why P1: Tail-drop drops all packets when queue is full. RED randomly drops packets before congestion. WRED uses IP precedence or DSCP to vary drop probability.
Variation 2. Which QoS mechanism is used to prevent head-of-line blocking by ensuring that a single queue does not consume all available buffer space?
medium- A.Policing
- B.Shaping
- ✓ C.Weighted Random Early Detection (WRED)
- D.Priority Queuing
Why C: Congestion avoidance mechanisms like Weighted Random Early Detection (WRED) proactively drop packets before queues become full, preventing tail drops and head-of-line blocking.
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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