The answer is that the policy-map does not specify a priority queue for latency-sensitive traffic. iSCSI is a storage protocol that demands strict priority queuing to maintain low latency and jitter, and without a priority queue configured in the QoS policy, all traffic—including iSCSI—is treated as best-effort, causing competition for bandwidth and resulting in high latency and drops even when iSCSI does not match the 'BulkData' class. On the Cisco DCCOR 350-601 exam, this question tests your understanding of QoS design for data center storage traffic, often appearing as a scenario where a candidate overlooks the need for a dedicated priority queue for protocols like iSCSI or FCoE. A common trap is assuming that simply classifying iSCSI into a separate class is sufficient, but without the priority command, no class receives expedited forwarding. Remember the memory tip: “iSCSI needs priority, not just classification—if it’s not in the fast lane, it’s stuck in traffic.”
350-601 Compute Practice Question
This 350-601 practice question tests your understanding of compute. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Refer to the exhibit. An engineer applies this QoS policy to a Cisco Nexus 9000 switch in a data center. After applying the policy, storage traffic (iSCSI) is experiencing high latency and occasional drops. The engineer verifies that the iSCSI traffic is not matching the 'BulkData' class. What is the most likely cause of the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy-map does not specify a priority queue for latency-sensitive traffic.
The correct answer is A because iSCSI is a latency-sensitive storage protocol that requires a strict priority queue to ensure low latency and minimal jitter. Without a priority queue configured in the policy-map, iSCSI traffic competes with other traffic classes on a best-effort basis, leading to high latency and drops even if it is not matching the 'BulkData' class.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The policy-map does not specify a priority queue for latency-sensitive traffic.
Why this is correct
iSCSI requires low latency; without a priority queue, it competes with other traffic.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The policy-map is applied at the system level, but iSCSI traffic is not classified under any class-map.
Why it's wrong here
iSCSI falls into class-default, but that doesn't cause drops; the lack of priority does.
✗
The bandwidth percent for class-default is too low, causing iSCSI to be starved.
Why it's wrong here
While 70% may be sufficient, the primary issue is lack of priority, not bandwidth starvation.
✗
The class-map 'BulkData' does not match the correct traffic because the match statement uses qos-group instead of dscp.
Why it's wrong here
Matching on qos-group is valid; the issue is not about matching.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that simply classifying traffic into a class-map is sufficient, but the trap here is that without a priority queue, latency-sensitive traffic like iSCSI will still suffer from high latency and drops even if correctly classified.
Detailed technical explanation
How to think about this question
In Cisco Nexus 9000 switches, MQC (Modular QoS CLI) allows defining class-maps and policy-maps, but latency-sensitive traffic like iSCSI must be assigned to a priority queue using the 'priority' command under the policy-map class. Without priority queuing, iSCSI traffic competes in the default queue with other traffic, causing buffer bloat and increased latency, especially under congestion. Real-world scenarios often involve storage traffic sharing links with backup or bulk data, where strict priority ensures iSCSI performance.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-601 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Compute — This question tests Compute — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The policy-map does not specify a priority queue for latency-sensitive traffic. — The correct answer is A because iSCSI is a latency-sensitive storage protocol that requires a strict priority queue to ensure low latency and minimal jitter. Without a priority queue configured in the policy-map, iSCSI traffic competes with other traffic classes on a best-effort basis, leading to high latency and drops even if it is not matching the 'BulkData' class.
What should I do if I get this 350-601 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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