350-501 Automation and Quality of Service Practice Question
A service provider is designing a QoS policy for a multi-service MPLS VPN network that carries voice, video, and data traffic. The network uses DiffServ and MPLS EXP markings. The design must ensure that voice traffic is given priority over video and data, while video traffic should have better treatment than data but not at the expense of voice. The provider plans to use a hierarchical QoS (HQoS) policy at the PE-CE interfaces. Which configuration approach best meets these requirements?
⚠ Common exam trap
Cisco often tests the misconception that a single-level LLQ can handle multiple priority classes together, but the trap here is that combining voice and video in one LLQ queue violates the strict priority requirement for voice over video, which HQoS with separate child policies resolves.
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
✓
Apply a parent policy with a shape for the total bandwidth and a child policy with LLQ for voice and CBWFQ for video and data.
Hierarchical QoS (HQoS) allows the service provider to enforce a total bandwidth shape at the parent level while using a child policy to apply LLQ for voice (ensuring strict priority) and CBWFQ for video and data (ensuring video gets better treatment than data without starving voice). This meets the requirement that video should not degrade voice, as the parent shape prevents any single class from monopolizing the link, and the child policy’s LLQ guarantees voice priority over all other 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.
- ✗
Mark voice traffic with EXP 5, video with EXP 4, and data with EXP 0, and rely on the core to prioritize based on EXP.
Why it's wrong here
Marking alone does not provide queuing; the PE-CE interfaces need explicit policies.
- ✗
Use a single-level policy with LLQ for voice and video together, and CBWFQ for data.
Why it's wrong here
LLQ for both voice and video could cause voice to compete with video, violating the requirement that video not affect voice.
- ✓
Apply a parent policy with a shape for the total bandwidth and a child policy with LLQ for voice and CBWFQ for video and data.
Why this is correct
This provides hierarchical control, ensuring voice gets priority within the shaped bandwidth while video and data get fair treatment.
- ✗
Apply class-based shaping to each traffic class separately on the interface.
Why it's wrong here
Class-based shaping does not provide priority queuing; voice could still be delayed if its queue is full.
Go deeper
Related to this question
About these practice questions
One of 971 original 350-501 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.