350-401 Question 68
Single answerA network engineer is tasked with implementing a QoS policy to prioritize voice traffic over other types of traffic in an enterprise network. The engineer decides to use a class-based QoS policy with low latency queuing (LLQ). Which step is crucial to ensure voice traffic is prioritized properly without starving other traffic types?
- A
Configure the voice traffic class with a bandwidth reservation using the 'bandwidth' command.
- B
Apply the QoS policy to the interface in the inbound direction.
- C
Configure the voice traffic class with the 'priority' command and set a police rate.
- D
Use Weighted Fair Queuing (WFQ) instead of LLQ to avoid starving other traffic.
Show answer and explanation
Correct answer: C
Explanation
To prioritize voice traffic in a QoS policy, LLQ is commonly used as it provides strict priority queuing for traffic marked as high-priority (e.g., voice). The 'priority' command ensures that voice traffic is dequeued first while also applying a police rate to limit its bandwidth usage. This prevents high-priority traffic from starving lower-priority traffic, maintaining a balanced and efficient QoS implementation.
- A. Incorrect.
The 'bandwidth' command can reserve bandwidth for a traffic class, but it does not enforce strict prioritization for voice traffic, which is required in this scenario.
- B. Incorrect.
QoS policies for prioritizing traffic, especially LLQ, are typically applied in the outbound direction on the interface to manage traffic leaving the device. Thus, applying it in the inbound direction is incorrect.
- C. Correct.
The 'priority' command is essential for LLQ as it ensures that voice traffic is dequeued first. Setting a police rate with this command prevents voice traffic from monopolizing the available bandwidth, ensuring other traffic types are not starved.
- D. Incorrect.
WFQ is not as effective as LLQ when strict prioritization of traffic is required. LLQ specifically combines strict priority queuing with policing to handle priority traffic like voice.