CCNP Infrastructure Practice Question
A network engineer is configuring QoS on a Cisco IOS router. The engineer needs to ensure that packets marked with DSCP AF31 are placed into a queue that guarantees at least 30% of the interface bandwidth during congestion, while allowing other traffic to use any remaining bandwidth. Which configuration should be used?
⚠ Common exam trap
Candidates often confuse bandwidth guarantee commands like 'bandwidth percent' with priority or shaping commands that limit or prioritize traffic differently.
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
✓
policy-map QOS class AF31 bandwidth percent 30
The 'bandwidth percent 30' command in a policy map class guarantees that the class receives at least 30% of the interface bandwidth during congestion. This is part of CBWFQ and provides a minimum bandwidth guarantee, meeting the requirement while allowing other traffic to utilize remaining bandwidth.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
policy-map QOS class AF31 shape average percent 30
Why it's wrong here
The 'shape average percent 30' command shapes traffic to a maximum rate of 30% of the interface bandwidth, which limits the class to 30% and does not guarantee a minimum. Shaping is used to smooth traffic rates and is not appropriate for guaranteeing bandwidth. This would restrict AF31 rather than ensure it receives at least 30%.
- ✗
policy-map QOS class AF31 bandwidth remaining percent 30
Why it's wrong here
The 'bandwidth remaining percent' command allocates a percentage of the remaining bandwidth after priority traffic, not a guaranteed minimum of the interface bandwidth. It does not ensure that AF31 gets at least 30% of the total interface bandwidth during congestion. This command is used in a hierarchical policy and may not meet the requirement of a guaranteed minimum.
- ✓
policy-map QOS class AF31 bandwidth percent 30
Why this is correct
The 'bandwidth percent 30' command guarantees that the class AF31 receives at least 30% of the interface bandwidth during congestion. This is a CBWFQ configuration that provides a minimum bandwidth guarantee, ensuring that AF31 traffic is prioritized while allowing other classes to use the remaining bandwidth. It directly satisfies the requirement.
- ✗
policy-map QOS class AF31 priority percent 30
Why it's wrong here
The 'priority percent 30' command assigns a strict priority queue with a 30% bandwidth limit, which is intended for low-latency traffic like voice. It does not guarantee a minimum bandwidth for AF31; instead, it provides priority treatment and polices excess traffic. This could starve other queues and does not match the requirement for a guaranteed minimum without strict priority.
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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.