CCNP Architecture Practice Question
A network architect is designing a QoS policy for a Cisco Catalyst switch that must prioritize voice traffic over all other traffic, while ensuring that bulk data transfers do not starve other applications. The design requires strict priority for voice and a guaranteed minimum bandwidth for business-critical applications. Which two mechanisms should be used together to meet these requirements?
⚠ Common exam trap
Test-takers frequently confuse congestion avoidance mechanisms like WRED with queuing mechanisms, or assuming that legacy queuing methods provide the same integrated functionality as LLQ and CBWFQ.
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) and Class-Based Weighted Fair Queuing (CBWFQ)
LLQ and CBWFQ are used together to provide strict priority for voice traffic while guaranteeing bandwidth for other classes. LLQ places voice in a priority queue with a policed rate to prevent starvation, and CBWFQ allocates minimum bandwidth to business-critical applications, ensuring they are not starved by bulk data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Priority Queuing (PQ) and Custom Queuing (CQ)
Why it's wrong here
PQ provides strict priority but can starve lower-priority queues, and CQ provides round-robin bandwidth allocation without strict priority. While they can be combined, they are legacy mechanisms and do not offer the granularity and integration of LLQ and CBWFQ in modern Cisco IOS.
- ✓
Low Latency Queuing (LLQ) and Class-Based Weighted Fair Queuing (CBWFQ)
Why this is correct
LLQ provides a strict priority queue for voice, ensuring low latency and jitter. CBWFQ provides guaranteed bandwidth for other classes, such as business-critical applications, preventing starvation. Together, they meet the requirements by prioritizing voice while allocating minimum bandwidth to other traffic classes.
- ✗
Class-Based Marking and Policing
Why it's wrong here
Marking and policing are used to classify and rate-limit traffic but do not provide queuing prioritization or bandwidth guarantees. They are often used in conjunction with queuing mechanisms, but alone they cannot ensure strict priority for voice or minimum bandwidth for business-critical applications.
- ✗
Weighted Random Early Detection (WRED) and First-In First-Out (FIFO) queuing
Why it's wrong here
WRED is a congestion avoidance mechanism that drops packets probabilistically, and FIFO provides no prioritization or bandwidth guarantees. Neither mechanism provides strict priority for voice or guaranteed bandwidth for business-critical applications, so they do not meet the design requirements.
About these practice questions
Courseiva writes every 350-401 question from scratch — 1,923 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.