The answer is buffer-to-buffer credit exhaustion, which directly causes the BB_Credit zero condition and the resulting throughput drop from 16 Gbps to 4 Gbps. In Fibre Channel, BB_Credits represent the number of frames a port can send before needing an acknowledgment; when the count hits zero, the transmitter must pause, stalling data flow and severely limiting effective throughput. This scenario is a classic performance troubleshooting item on the Cisco DCCOR 350-601 exam, where you must distinguish credit exhaustion from link errors (which show CRC increments) or congestion (which manifests as latency or F_BSY frames). A common trap is to blame distance alone, but the root cause is an insufficient credit pool for the link’s round-trip time—often due to long-distance links without adequate buffer credits allocated. Memory tip: think “zero credits = zero flow” to recall that BB_Credit zero means the pipeline is empty and waiting.
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.
An administrator is troubleshooting a performance issue in an FC SAN. The initiator and target are in the same VSAN. The link is 16 Gbps but throughput is only 4 Gbps. The engineer checks the BB_Credit utilization and sees a high count of BB_Credit zero. What is the most likely cause?
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
✓
Buffer-to-buffer credit exhaustion
BB_Credit zero indicates buffer-to-buffer credit exhaustion, which pauses transmission and reduces throughput. This is typically due to distance or small credit pool. Link errors would show CRC errors, congestion would cause other symptoms, and zoning is unrelated.
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.
✗
Congestion on the target port
Why it's wrong here
Target port congestion would likely show other signs like high latency, not BB_Credit zero.
✗
High link error rates
Why it's wrong here
Link errors would show CRC or other error counters, not BB_Credit utilization.
✗
Incorrect zoning configuration
Why it's wrong here
Zoning affects connectivity, not throughput on a working link.
✓
Buffer-to-buffer credit exhaustion
Why this is correct
BB_Credit zero means the port has run out of credits, causing pauses and low throughput.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
Target port congestion would likely show other signs like high latency, not BB_Credit zero.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 350-601 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Buffer-to-buffer credit exhaustion — BB_Credit zero indicates buffer-to-buffer credit exhaustion, which pauses transmission and reduces throughput. This is typically due to distance or small credit pool. Link errors would show CRC errors, congestion would cause other symptoms, and zoning is unrelated.
What should I do if I get this 350-601 question wrong?
Identify which 350-601 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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