Quick Answer
Low Latency Queuing (LLQ) is the correct choice because it combines Class-Based Weighted Fair Queuing (CBWFQ) with a strict priority queue, ensuring that voice traffic marked with EF or CS5 is always dequeued before any other traffic class. This mechanism guarantees low latency and jitter for real-time traffic, which is essential for maintaining voice quality in a converged network. On the ENCOR 350-401 exam, this concept frequently appears in QoS design scenarios where you must distinguish LLQ from other queuing methods like WFQ or CBWFQ alone—the common trap is assuming CBWFQ provides priority, but it only guarantees bandwidth, not strict priority. Remember that LLQ is the only Cisco queuing tool that offers a true priority queue for delay-sensitive traffic. A helpful memory tip: think of LLQ as "LLQ = CBWFQ + a VIP lane" where voice always cuts to the front of the line.
This 350-401 practice question tests your understanding of architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is implementing QoS in a network where voice traffic must have strict priority over all other traffic. Which queuing mechanism should be used on the outbound interface of a router to ensure voice packets are always sent first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Clue: "always"
Why it matters: Absolute qualifier. An answer using 'always' is only correct if there are genuinely no exceptions — absolute statements are often wrong in networking.
Random Early Detection (RED)
Why wrong: RED is a congestion avoidance mechanism, not a queuing mechanism.
Low Latency Queuing (LLQ)
LLQ combines a strict priority queue with CBWFQ, ensuring voice gets priority.
First In First Out (FIFO)
Why wrong: FIFO does not prioritize any traffic.
Class-Based Weighted Fair Queuing (CBWFQ)
Why wrong: CBWFQ assigns bandwidth weights but does not guarantee strict priority.
Answer choices
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) is the correct choice because it combines Class-Based Weighted Fair Queuing (CBWFQ) with a strict priority queue, ensuring that voice traffic (marked with EF or CS5) is always dequeued before any other traffic class. This guarantees low latency and jitter for real-time traffic, which is essential for voice quality.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Random Early Detection (RED)
Why it's wrong here
RED is a congestion avoidance mechanism, not a queuing mechanism.
Low Latency Queuing (LLQ)
Why this is correct
LLQ combines a strict priority queue with CBWFQ, ensuring voice gets priority.
Clue confirmation
The clue words "first", "always" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
First In First Out (FIFO)
Why it's wrong here
FIFO does not prioritize any traffic.
Class-Based Weighted Fair Queuing (CBWFQ)
Why it's wrong here
CBWFQ assigns bandwidth weights but does not guarantee strict priority.
Common exam traps
Cisco often tests the distinction between CBWFQ and LLQ, trapping candidates who think CBWFQ alone provides priority queuing, when in fact LLQ is required to add the strict priority queue for real-time traffic.
Detailed technical explanation
LLQ implements a strict priority queue by using a policer (typically configured with the 'priority' command under a class map) that limits the amount of traffic allowed into the priority queue to prevent starvation of other queues. In real-world deployments, voice traffic is marked with DSCP EF (46) and placed into the priority queue, while the router uses a tail-drop mechanism for the priority queue when the policer threshold is exceeded, ensuring that non-voice traffic still gets service.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Architecture — study guide chapter
Learn the concepts, then practise the questions
Architecture practice questions
Targeted practice on this topic area only
All 350-401 questions
2,015 questions across all exam domains
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise 350-401 questions linked to Architecture.
Practise 350-401 questions linked to Enterprise Network Design.
Practise 350-401 questions linked to SD-Access Architecture.
Practise 350-401 questions linked to SD-WAN Architecture.
Practise 350-401 questions linked to QoS Architecture.
Practise 350-401 questions linked to Virtualization.
Practise 350-401 questions linked to Network Function Virtualization.
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
Practise 350-401 questions linked to VRF and Path Isolation.
Practise 350-401 questions linked to Infrastructure.
Practise 350-401 questions linked to OSPF.
Practise 350-401 questions linked to BGP.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Architecture — This question tests Architecture — Read the scenario before looking for a memorised answer..
The correct answer is: Low Latency Queuing (LLQ) — Low Latency Queuing (LLQ) is the correct choice because it combines Class-Based Weighted Fair Queuing (CBWFQ) with a strict priority queue, ensuring that voice traffic (marked with EF or CS5) is always dequeued before any other traffic class. This guarantees low latency and jitter for real-time traffic, which is essential for voice quality.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "first", "always". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
Last reviewed: Jun 11, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.