This 350-501 practice question tests your understanding of services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 customer is experiencing packet loss during congestion on a link. The service provider wants to implement a QoS policy that drops less important traffic before more important traffic. Which queuing mechanism is best suited?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Class-Based Weighted Fair Queuing (CBWFQ) with WRED
CBWFQ allocates bandwidth per class, WRED drops low priority before high priority.
FIFO queuing
Why wrong: FIFO does not differentiate traffic.
Low Latency Queuing (LLQ)
Why wrong: LLQ provides strict priority, not selective drop.
Traffic shaping
Why wrong: Shaping buffers excess traffic, does not drop preferentially.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Class-Based Weighted Fair Queuing (CBWFQ) with WRED
CBWFQ with WRED is the best choice because CBWFQ provides per-class queuing with guaranteed bandwidth, while WRED proactively drops less important traffic (based on IP precedence or DSCP) before the queue becomes full, preventing tail drop and ensuring that higher-priority traffic is preserved during congestion. This combination allows the service provider to selectively discard lower-priority packets under congestion, meeting the requirement to drop less important traffic before more important traffic.
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.
Class-Based Weighted Fair Queuing (CBWFQ) with WRED
Why this is correct
CBWFQ allocates bandwidth per class, WRED drops low priority before high priority.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
FIFO queuing
Why it's wrong here
FIFO does not differentiate traffic.
Low Latency Queuing (LLQ)
Why it's wrong here
LLQ provides strict priority, not selective drop.
Traffic shaping
Why it's wrong here
Shaping buffers excess traffic, does not drop preferentially.
Common exam traps
Cisco often tests the misconception that LLQ alone can prioritize traffic during congestion, but the trap here is that LLQ provides strict priority queuing without proactive dropping, so it does not selectively drop less important traffic; WRED is required for that function.
Detailed technical explanation
WRED uses an exponential weighted average to calculate the average queue depth and begins dropping packets probabilistically when the average exceeds a minimum threshold, with drop probability increasing up to a maximum threshold. In a CBWFQ context, WRED can be configured per class with different drop profiles based on DSCP or IP precedence, allowing granular control over which packets are dropped first. A real-world scenario is a service provider offering multiple SLAs (e.g., gold, silver, bronze) over a single link, where WRED ensures gold traffic is rarely dropped while bronze traffic is shed first under congestion.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Services — study guide chapter
Learn the concepts, then practise the questions
Services practice questions
Targeted practice on this topic area only
All 350-501 questions
500 questions across all exam domains
Cisco SPCOR / CCNP Service Provider Core 350-501 study guide
Full concept coverage aligned to exam objectives
350-501 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 350-501 questions linked to Architecture.
Practise 350-501 questions linked to Networking.
Practise 350-501 questions linked to MPLS and Segment Routing.
Practise 350-501 questions linked to Automation and Quality of Service.
Practise 350-501 questions linked to Services.
Practise 350-501 questions linked to Automation and Assurance.
Practise 350-501 questions linked to 350-501 fundamentals.
Practise 350-501 questions linked to 350-501 scenario.
Practise 350-501 questions linked to 350-501 troubleshooting.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Services — This question tests Services — Read the scenario before looking for a memorised answer..
The correct answer is: Class-Based Weighted Fair Queuing (CBWFQ) with WRED — CBWFQ with WRED is the best choice because CBWFQ provides per-class queuing with guaranteed bandwidth, while WRED proactively drops less important traffic (based on IP precedence or DSCP) before the queue becomes full, preventing tail drop and ensuring that higher-priority traffic is preserved during congestion. This combination allows the service provider to selectively discard lower-priority packets under congestion, meeting the requirement to drop less important traffic before more important traffic.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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 →
Last reviewed: Jun 25, 2026
This 350-501 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 350-501 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.