CCNP Architecture Practice Question
A network engineer is designing a QoS policy for a Cisco Catalyst switch that will carry voice, video, and data traffic. The engineer wants to ensure that voice traffic receives strict priority queuing, video traffic gets guaranteed bandwidth, and data traffic uses leftover bandwidth. The switch supports Cisco Modular QoS CLI (MQC). Which queuing mechanism should be configured on the egress interface to meet these requirements?
⚠ Common exam trap
A common mix-up: candidates confuse CBWFQ with LLQ, or thinking that WRED provides queuing. LLQ is specifically designed for low-latency traffic like voice.
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
✓
Low Latency Queuing (LLQ)
LLQ is the correct queuing mechanism because it combines strict priority queuing for voice with guaranteed bandwidth for other classes like video. It is configured using MQC with a priority command for voice and bandwidth commands for other classes. CBWFQ lacks strict priority, WRED is a congestion avoidance tool, and FIFO provides no differentiation. Thus, LLQ meets all the stated requirements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
First-In, First-Out (FIFO) queuing
Why it's wrong here
FIFO queuing processes packets in the order they arrive without any prioritization or bandwidth guarantees. It does not differentiate between voice, video, and data traffic. This would not meet the requirement for strict priority for voice or guaranteed bandwidth for video. Hence, FIFO is not the correct queuing mechanism for this scenario.
- ✗
Class-Based Weighted Fair Queuing (CBWFQ)
Why it's wrong here
CBWFQ provides guaranteed bandwidth to classes but does not offer strict priority queuing. While it can allocate bandwidth to voice, it cannot guarantee low latency and jitter for voice traffic because it uses weighted fair queuing rather than a priority queue. Since the requirement explicitly states strict priority for voice, CBWFQ alone is insufficient. Thus, it is not the correct answer.
- ✓
Low Latency Queuing (LLQ)
Why this is correct
LLQ provides strict priority queuing for voice traffic while allowing other classes to have guaranteed bandwidth. It is configured using the priority command within a policy map applied to the interface. This meets the requirement for voice to have strict priority, video to have guaranteed bandwidth (using bandwidth command), and data to use leftover bandwidth. Therefore, LLQ is the correct queuing mechanism for this scenario.
- ✗
Weighted Random Early Detection (WRED)
Why it's wrong here
WRED is a congestion avoidance mechanism that drops packets based on queue thresholds to prevent tail drop. It does not provide queuing or bandwidth guarantees; it works in conjunction with queuing mechanisms. It cannot ensure strict priority for voice or guaranteed bandwidth for video. Therefore, WRED is not the correct queuing mechanism for this requirement.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.