CCNP Architecture Practice Question
A network engineer is designing a QoS policy for a WAN edge router. The requirement is to ensure that VoIP traffic receives strict priority treatment and that excess VoIP traffic is policed to prevent starvation of other traffic. Which QoS mechanism should be used?
⚠ Common exam trap
The trap here is assuming that CBWFQ provides strict priority, when it actually only guarantees bandwidth without prioritizing delay-sensitive traffic.
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)
Low Latency Queuing (LLQ) combines strict priority queuing with a policer. The priority queue ensures VoIP packets are transmitted before other traffic, minimizing delay and jitter. The policer limits the amount of traffic that can enter the priority queue, preventing VoIP from consuming all bandwidth and starving other applications. This dual behavior exactly matches the requirement for strict priority treatment with excess VoIP policing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Low Latency Queuing (LLQ)
Why this is correct
Low Latency Queuing (LLQ) provides strict priority queuing for delay-sensitive traffic like VoIP. It includes a policer that limits the priority queue to a configured bandwidth, preventing it from starving other queues. This matches the requirement for strict priority treatment with policing of excess VoIP traffic, making it the correct choice.
- ✗
Class-Based Weighted Fair Queuing (CBWFQ)
Why it's wrong here
CBWFQ provides weighted fair queuing for different traffic classes but does not offer strict priority. It guarantees bandwidth but does not prioritize VoIP traffic above all others. Without a priority queue, VoIP packets may experience delays, so CBWFQ alone does not meet the strict priority requirement.
- ✗
Weighted Random Early Detection (WRED)
Why it's wrong here
WRED is a congestion avoidance mechanism that drops packets based on queue thresholds. It does not provide strict priority queuing or policing. While it can help manage congestion, it does not ensure VoIP traffic receives priority treatment, so it is not suitable for this scenario.
- ✗
Traffic Shaping
Why it's wrong here
Traffic shaping delays packets to smooth traffic bursts, which can introduce latency. It is not a priority queuing mechanism and does not provide strict priority for VoIP. Shaping is typically used to conform to a contracted rate, not to prioritize voice traffic, so it fails the 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
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