Configuring a Cisco UCS QoS System Class with No-Drop and Jumbo MTU
Implement Cisco Unified Compute System Blade Chassis
AnswerCorrect answer: C — Create a QoS system class and specify an MTU value of 9216 bytes.
A QoS policy on Cisco UCS must meet these requirements: • No-drop class must be configured. • Jumbo frames must be enabled without fragmentation. Which configuration must be implemented to mast these conditions?
Configure slow-drain timers and specify an MTU value of 9100 bytes.
Create a Flow Control Policy and specify an MTU value of 9000 bytes.
Create a QoS system class and specify an MTU value of 9216 bytes. Correct Answer
Configure Platinum system class and specify an MTU value of 9100 bytes.
Community Votes
C
75%
D
25%
75% of anonymous learners picked answer C.
Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
No-drop is a property of a QoS system class, not a separate flow-control policy. When a no-drop class is configured you set its MTU (up to 9216) to support jumbo frames without fragmentation; the Fibre Channel system class is no-drop by default.
In UCS Manager, no-drop classes (e.g., for FCoE) are enabled under QoS System Class (LAN > LAN Cloud). The MTU is configurable only for no-drop classes and maxes at 9216 bytes; drop classes are fixed and not user-set.
Picking the Platinum system class (D) or a Flow Control Policy (B). Platinum is one no-drop class but the question asks for the configuration meeting both conditions; the precise object is the QoS system class with MTU 9216. A flow control policy sets PFC, not the no-drop class plus MTU.
Community Discussion (3 comments)
SYME👍 1
C: System class: Fibre Channel A system class that sets the quality of service for the lane reserved for Fibre Channel over Ethernet traffic. Some properties of this system class are preset and cannot be modified. For example, this class has a no-drop policy that ensures it never drops data packets. You cannot disable this system class. https://www.cisco.com/en/US/docs/unified_computing/ucs/sw/cli/config/guide/1.4.1/CLI_Config_Guide_1_4_1_chapter17.html#task_8355257724788063901
madelesm👍 3Selected: C
C, no drop can be assigned to any class
asd248402👍 1Selected: D
no drop mean platinum that is the only one to guarantee the no drop
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Expert Analysis
Why the Answer Is Correct
Cisco UCS QoS is implemented through system classes (LAN > LAN Cloud > QoS System Class). To meet a no-drop requirement and enable jumbo frames, you create/enable a QoS system class, mark it no-drop, and set its MTU to 9216 bytes. The MTU is only user-configurable for no-drop classes, with a maximum of 9216.
Why the Other Options Are Wrong
A. Slow-drain timers plus MTU 9100 is not the UCS QoS mechanism for no-drop; slow-drain is a SAN feature. B. A Flow Control Policy configures priority-flow-control but does not create the no-drop system class with a configurable MTU. D. Platinum is a specific no-drop class but uses the wrong MTU value (9100) and is less general than "create a QoS system class."
Community Comment Notes
Community: "C, no drop can be assigned to any class." Another note: the FC system class has a no-drop policy preset and "MTU is only configurable for no-drop type QoS system classes" with max 9216. Votes C 75 / D 25.