350-501 Automation and Quality of Service Practice Question
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?
⚠ Common exam trap
Cisco often tests the misconception that a taildrop threshold alone indicates congestion, when in fact the average queue depth is the direct indicator of how much traffic is buffered and thus the level of congestion.
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
✓
Best-effort class, because its average depth is 580.
The exhibit shows that the best-effort class has an average queue depth of 580 packets, which is significantly higher than the voice class's average depth. This indicates that the best-effort class is experiencing the most congestion, as queue depth is a direct measure of buffered packets waiting for transmission. The voice class, despite having a taildrop threshold, has a much lower average depth, showing it is not as congested.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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