350-501 Services Practice Question
A customer is experiencing packet loss during congestion on a link. The service provider wants to implement a QoS policy that drops less important traffic before more important traffic. Which queuing mechanism is best suited?
⚠ Common exam trap
Cisco often tests the misconception that LLQ alone can prioritize traffic during congestion, but the trap here is that LLQ provides strict priority queuing without proactive dropping, so it does not selectively drop less important traffic; WRED is required for that function.
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
✓
Class-Based Weighted Fair Queuing (CBWFQ) with WRED
CBWFQ with WRED is the best choice because CBWFQ provides per-class queuing with guaranteed bandwidth, while WRED proactively drops less important traffic (based on IP precedence or DSCP) before the queue becomes full, preventing tail drop and ensuring that higher-priority traffic is preserved during congestion. This combination allows the service provider to selectively discard lower-priority packets under congestion, meeting the requirement to drop less important traffic before more important traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Class-Based Weighted Fair Queuing (CBWFQ) with WRED
Why this is correct
CBWFQ allocates bandwidth per class, WRED drops low priority before high priority.
- ✗
FIFO queuing
Why it's wrong here
FIFO does not differentiate traffic.
- ✗
Low Latency Queuing (LLQ)
Why it's wrong here
LLQ provides strict priority, not selective drop.
- ✗
Traffic shaping
Why it's wrong here
Shaping buffers excess traffic, does not drop preferentially.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.