350-601 Compute Practice Question
Exhibit
UCS Manager > Service Profile > vNIC List vNIC Name: eth0 Fabric ID: A Adapter Policy: Windows MTU: 9000 VLAN: 100 (Native) UCS Manager > LAN > LAN Cloud > QoS System Class Class-FC: No Drop, MTU 9216, Weight 10 Class-Platinum: Drop, MTU 9216, Weight 30 Class-Gold: Drop, MTU 1500, Weight 20 Class-Silver: Drop, MTU 1500, Weight 10 Class-Bronze: Drop, MTU 1500, Weight 5
Refer to the exhibit. A server with vNIC eth0 is experiencing packet drops on its Ethernet interface. The server is sending jumbo frames (MTU 9000) on VLAN 100. The QoS system class 'Class-Platinum' has an MTU of 9216 and is configured with 'Drop'. The vNIC is not assigned to any QoS policy. What is the most likely reason for the drops?
⚠ Common exam trap
Cisco often tests the misconception that a system class with a higher MTU (like Class-Platinum) automatically applies to all traffic, when in fact the vNIC must be explicitly mapped to that QoS policy to use it.
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
✓
The vNIC is not mapped to a QoS policy, so it uses the default best-effort class which has an MTU of 1500 and drops jumbo frames.
When a vNIC is not assigned to a QoS policy, it defaults to the best-effair class, which typically has an MTU of 1500 bytes. Since the server is sending jumbo frames (MTU 9000) on VLAN 100, these frames exceed the default MTU and are dropped at the Ethernet interface. The 'Class-Platinum' system class with MTU 9216 is irrelevant because the vNIC is not mapped to it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The vNIC is not mapped to a QoS policy, so it uses the default best-effort class which has an MTU of 1500 and drops jumbo frames.
Why this is correct
Without a QoS policy, the default class (often Bronze) applies, which has MTU 1500.
- ✗
The QoS system class for jumbo frames requires a 'No Drop' policy to avoid drops.
Why it's wrong here
Drop policy is not the issue; MTU mismatch is.
- ✗
The server is sending frames larger than 9216 bytes.
Why it's wrong here
The server is sending MTU 9000, which is within 9216.
- ✗
The native VLAN setting on the vNIC causes the QoS system class to be ignored.
Why it's wrong here
Native VLAN does not affect QoS classification.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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