350-401 Infrastructure Practice Question
A network engineer is configuring a Cisco IOS router for QoS and wants to ensure that voice traffic is prioritized and that excess traffic is dropped rather than buffered when congestion occurs. The engineer decides to use Low Latency Queueing (LLQ). Which two statements accurately describe the behavior of LLQ? (Choose two.)
⚠ Common exam trap
The trap here is assuming that LLQ allows multiple priority queues or that it buffers excess priority traffic, when in fact it supports only one priority queue and drops excess packets via a policer.
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
✓
LLQ provides a strict priority queue that is serviced before other queues, ensuring low latency for voice traffic.
LLQ provides a single strict priority queue that is serviced before other queues, ensuring low latency for voice. It uses a policer to cap the priority queue's bandwidth, dropping excess packets to prevent starvation of other queues. These two characteristics are fundamental to LLQ's operation and make it suitable for real-time traffic while maintaining fairness.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
LLQ provides a strict priority queue that is serviced before other queues, ensuring low latency for voice traffic.
Why this is correct
LLQ includes a strict priority queue that is always serviced first when packets are present, which minimizes delay and jitter for voice. This is a key characteristic of LLQ, making it suitable for real-time traffic. The priority queue is typically configured with a bandwidth guarantee and a policer to limit its maximum rate, preventing starvation of other queues.
- ✗
LLQ can be configured only on interfaces that support hardware queuing, such as serial interfaces.
Why it's wrong here
LLQ is a software queuing mechanism that can be applied to various interface types, including Ethernet, serial, and others. It is not restricted to hardware queuing interfaces. While some platforms may have hardware acceleration, the fundamental LLQ feature is available on a wide range of Cisco IOS routers and interfaces. Thus, this statement is false.
- ✗
LLQ buffers all excess traffic in the priority queue until bandwidth becomes available, ensuring no packets are dropped.
Why it's wrong here
LLQ does not buffer excess traffic in the priority queue; instead, it drops packets that exceed the configured rate. This is intentional to avoid delay and jitter for the priority traffic. Buffering excess voice packets would increase latency, which is undesirable. Therefore, this statement is incorrect.
- ✓
LLQ uses a policer to limit the amount of traffic that can enter the priority queue, dropping excess packets.
Why this is correct
LLQ employs a policer (often called the priority policer) to enforce the configured bandwidth limit for the priority queue. Traffic exceeding this limit is dropped, which prevents the priority queue from consuming all bandwidth and starving other queues. This policer is a key mechanism in LLQ to maintain fairness and control congestion.
- ✗
LLQ allows multiple priority queues to be configured, each with its own bandwidth guarantee.
Why it's wrong here
LLQ supports only a single strict priority queue within a policy map. Configuring multiple priority queues is not allowed; only one class can be designated as priority. This limitation ensures that the priority queue does not starve other queues. Therefore, this statement is false.
Go deeper
Related to this question
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.