350-401 Architecture Practice Question
A network architect is selecting a switching platform for a data center access layer that must support lossless Ethernet for FCoE. The platform must provide per-priority flow control so that storage traffic can be paused without affecting LAN traffic. Which technology should the architect specify?
⚠ Common exam trap
The trap here is assuming that enabling jumbo frames or EtherChannel is sufficient for lossless FCoE, when only a per-priority pause mechanism prevents drops for the storage class.
Answer choices
Why each option matters
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)
Lossless Ethernet for FCoE requires a mechanism that can pause a specific traffic class without stopping all traffic on the link. Priority Flow Control does exactly that by acting on CoS values, allowing storage frames to be paused while ordinary LAN traffic continues. LLDP, EtherChannel, and jumbo frames each address different concerns and none provides per-priority pause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
EtherChannel with LACP
Why it's wrong here
EtherChannel with LACP bundles multiple physical links into one logical link for increased bandwidth and redundancy. It does not provide per-priority flow control; if a member link becomes congested, traffic can be affected across the bundle. LACP is a link aggregation control protocol and has no mechanism to pause a specific CoS priority for lossless storage traffic.
- ✗
Jumbo frame support
Why it's wrong here
Jumbo frames increase the MTU to reduce per-packet overhead, which benefits bulk storage throughput but does not prevent frame drops during congestion. Without a pause mechanism, a burst can still overflow a queue and cause drops that break FCoE. Jumbo frames alone cannot deliver the lossless behavior required for Fibre Channel over Ethernet.
- ✓
Priority Flow Control (PFC)
Why this is correct
PFC is the correct choice because it operates on IEEE 802.1Q CoS priorities and allows a receiver to send a PAUSE frame for a specific priority, pausing only the storage class of traffic while LAN traffic on other priorities continues unimpeded. This satisfies the requirement for lossless FCoE without head-of-line blocking across the entire link.
- ✗
Link Layer Discovery Protocol (LLDP)
Why it's wrong here
LLDP is a neighbor discovery protocol used to advertise device identity, capabilities, and management addresses. It carries no flow-control semantics and cannot pause frames or differentiate traffic classes. While LLDP may be used to negotiate DCBX parameters that carry PFC configuration, LLDP itself does not provide the per-priority pause behavior required for lossless FCoE.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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