The correct answer is to ensure sufficient buffer allocation for the no-drop class. This directly addresses the queuing drops on FCoE because Fibre Channel over Ethernet requires a lossless fabric, enforced by Priority Flow Control (PFC) on the no-drop class. When buffer exhaustion occurs during peak traffic, the no-drop class cannot absorb bursts, leading to the very drops that violate FCoE’s lossless guarantee. On the Cisco DCCOR 350-601 exam, this scenario tests your understanding of QoS buffer allocation as a critical component of data center storage networking, often appearing in a troubleshooting context where you must differentiate between buffer tuning and other QoS actions like shaping or policing. A common trap is to assume that increasing overall interface bandwidth or adjusting scheduling weights will fix the drops, but the root cause is specifically buffer starvation in the lossless class. Memory tip: think “no-drop needs no-starve”—if FCoE frames are dropping, the no-drop class buffer is the first place to allocate more.
350-601 Storage Network Practice Question
This 350-601 practice question tests your understanding of storage network. 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.
A data center uses FCoE on Nexus 9000 switches. The storage team reports inconsistent performance during peak times. Queuing drops are seen on the FCoE-enabled interfaces. Which QoS configuration change would best address the issue?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Ensure sufficient buffer allocation for the no-drop class
In FCoE networks, lossless behavior is required for storage traffic, which is enforced by priority flow control (PFC) on the no-drop class. Queuing drops on FCoE-enabled interfaces indicate that the no-drop class is experiencing buffer exhaustion under congestion. Increasing buffer allocation for the no-drop class ensures that FCoE frames are not dropped, maintaining the lossless fabric required by Fibre Channel over Ethernet.
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.
Ensure sufficient buffer allocation for the no-drop class
Why this is correct
Correct: Allocating more buffers to the no-drop class prevents drops.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the number of pause frames on the no-drop class
Why it's wrong here
Incorrect: More pause frames can lead to congestion spreading.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that pause frames alone guarantee lossless delivery, but the trap is that insufficient buffer allocation for the no-drop class will still cause drops under burst conditions, regardless of pause frame configuration.
Detailed technical explanation
How to think about this question
FCoE relies on PFC (IEEE 802.1Qbb) to create a no-drop class by pausing the sender when the receive buffer is near capacity. However, if the buffer is undersized for the traffic burst, the pause mechanism cannot prevent drops because the buffer overflows before the sender stops. On Nexus 9000 switches, the 'class-fcoe' policy-map can be tuned with the 'priority-flow-control' command and buffer allocation via 'hardware qos' or 'class-map' buffer settings; a common best practice is to allocate at least 50% of the port buffer to the no-drop class for FCoE traffic.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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.
Storage Network — This question tests Storage Network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Ensure sufficient buffer allocation for the no-drop class — In FCoE networks, lossless behavior is required for storage traffic, which is enforced by priority flow control (PFC) on the no-drop class. Queuing drops on FCoE-enabled interfaces indicate that the no-drop class is experiencing buffer exhaustion under congestion. Increasing buffer allocation for the no-drop class ensures that FCoE frames are not dropped, maintaining the lossless fabric required by Fibre Channel over Ethernet.
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: "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.
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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