This 350-601 practice question tests your understanding of storage network. 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 network engineer is deploying FCoE in a top-of-rack design. Which statement about the required lossless Ethernet fabric is correct?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Priority Flow Control (PFC) must be enabled to create lossless CoS
Option A is correct: Priority Flow Control (PFC) is mandatory for FCoE to ensure no frames are dropped due to congestion. Option B is wrong because DCBX is used to negotiate PFC, but PFC itself is the mechanism. Option C is wrong: FCoE uses a dedicated VLAN (typically 1002–1003 but can be assigned). Option D is wrong: FCoE maximum frame size is 2240 bytes (or 2500 with jumbo).
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Data Center Bridging Exchange (DCBX) automatically enables PFC when FCoE is configured
Why it's wrong here
DCBX advertises and negotiates PFC, but PFC must be explicitly enabled.
✗
FCoE uses VLAN 1002 by default for all traffic
Why it's wrong here
VLAN assignment is configurable, though default VSANs map to VLAN 1002-1003.
✗
FCoE frames are limited to 1500 bytes to avoid fragmentation
Why it's wrong here
FCoE requires jumbo frames up to 2500 bytes typically.
✓
Priority Flow Control (PFC) must be enabled to create lossless CoS
Why this is correct
PFC ensures lossless behavior for FCoE frames.
Related concept
Access ports place end devices into a single VLAN.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-601 questions on switching, trunking, and access-port configuration.
Storage Network — This question tests Storage Network — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Priority Flow Control (PFC) must be enabled to create lossless CoS — Option A is correct: Priority Flow Control (PFC) is mandatory for FCoE to ensure no frames are dropped due to congestion. Option B is wrong because DCBX is used to negotiate PFC, but PFC itself is the mechanism. Option C is wrong: FCoE uses a dedicated VLAN (typically 1002–1003 but can be assigned). Option D is wrong: FCoE maximum frame size is 2240 bytes (or 2500 with jumbo).
What should I do if I get this 350-601 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-601 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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