The answer is the best-effort class, because its average queue depth of 580 is dangerously close to the tail-drop threshold of 600, and its maximum depth of 650 has already exceeded that threshold, confirming packet drops. Interpreting queue depth statistics for congestion requires comparing average and maximum depths against configured thresholds; a queue consistently near or over its threshold indicates sustained congestion and active tail drops, while low depths like the voice class show no pressure. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this tests your ability to read output from commands like show policy-map interface and correlate queue depths with drop counts—a common trap is mistaking a high instantaneous max for congestion without checking the average depth against the threshold. Remember the memory tip: “Average near the edge, max over the ledge” to quickly identify the congested class.
350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. 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.
Exhibit
Refer to the exhibit.
RP/0/0/CPU0:router# show qos interface gigabitEthernet 0/0/0/0
Interface: GigabitEthernet0/0/0/0
Bandwidth configured: 1000000 kbps
Policy: QOS_BUSINESS
Class: VOICE
Queue ID: 1
Taildrop thresholds: 50 packets
Average queue depth: 12 packets
Maximum queue depth: 48 packets
Class: BEST_EFFORT
Queue ID: 2
Taildrop thresholds: 600 packets
Average queue depth: 580 packets
Maximum queue depth: 650 packets
Refer to the exhibit. An engineer monitors the queue depths on a core interface. Which class is experiencing the most congestion?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Best-effort class, because its average depth is 580.
Option D is correct. Best-effort queue has average depth 580 near its taildrop threshold of 600, and max depth 650 which exceeds the threshold, indicating drops. Voice queue depth is low. Option A is wrong because voice is under threshold. Option B is wrong because best-effort is near threshold. Option C is wrong because the command already shows the data.
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 interface is not congested because bandwidth is 1 Gbps.
Why it's wrong here
Congestion is determined by queue depth, not total bandwidth.
✗
Voice class, because it has a taildrop threshold.
Why it's wrong here
Voice depth is far below threshold.
✗
Both classes equally, because they both have taildropping.
Why it's wrong here
Voice is not congested.
✓
Best-effort class, because its average depth is 580.
Why this is correct
Correct: Nearly at taildrop threshold of 600, and exceeded max.
Related concept
Read the scenario before looking for a memorised answer.
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 350-501 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 350-501 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.
Automation and Quality of Service — This question tests Automation and Quality of Service — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Best-effort class, because its average depth is 580. — Option D is correct. Best-effort queue has average depth 580 near its taildrop threshold of 600, and max depth 650 which exceeds the threshold, indicating drops. Voice queue depth is low. Option A is wrong because voice is under threshold. Option B is wrong because best-effort is near threshold. Option C is wrong because the command already shows the data.
What should I do if I get this 350-501 question wrong?
Identify which 350-501 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.
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Question Discussion
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