The answer is that the physical NIC’s PF is also used for the host management network, and SR-IOV configuration disrupted it. When SR-IOV is enabled, the Physical Function (PF) is shared between the host’s management stack and the Virtual Functions (VFs) assigned to VMs. If the same NIC handles both management traffic and SR-IOV VFs, the PF driver can become unstable or lose its configuration, making the management network unreachable even though the VF-based VM still communicates. On the ENCOR 350-401 exam, this scenario tests your understanding of SR-IOV architecture and the critical distinction between PF and VF roles—a common trap is assuming VFs operate independently without affecting the PF. Remember the memory tip: “PF is the host’s lifeline; don’t let SR-IOV cut it.”
CCNP Virtual Machines and Hypervisors Practice Question
This 350-401 practice question tests your understanding of virtual machines and hypervisors. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 company is deploying a virtualized firewall on a VMware ESXi host. The firewall VM requires high network throughput and low latency. The engineer decides to use SR-IOV to assign a virtual function (VF) from a physical NIC to the VM. After configuration, the VM can communicate, but the host's management network becomes unreachable. 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
✓
The physical NIC's PF is also used for the host management network, and SR-IOV configuration disrupted it.
When SR-IOV is enabled on a physical NIC, the Physical Function (PF) is shared between the host management network and the Virtual Functions (VFs). If the PF is used for the host management network, enabling SR-IOV can disrupt the PF's driver or configuration, causing the management network to become unreachable. This is a common misconfiguration where the same NIC is used for both management and SR-IOV VFs.
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.
✓
The physical NIC's PF is also used for the host management network, and SR-IOV configuration disrupted it.
Why this is correct
Correct because SR-IOV can interfere with the PF if the management network is on the same port.
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.
✗
The VM's VF is using the same MAC address as the host management interface.
Why it's wrong here
Incorrect because SR-IOV assigns unique MAC addresses to VFs.
✗
The ESXi host requires a dedicated physical NIC for management when using SR-IOV.
Why it's wrong here
Incorrect because SR-IOV can coexist with management on the same NIC if properly configured.
✗
The VM's VF is consuming all available bandwidth on the NIC.
Why it's wrong here
Incorrect because bandwidth consumption would not cause the management network to become unreachable.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that SR-IOV requires a dedicated management NIC, but the real issue is that the same PF cannot serve both management and SR-IOV VFs without disruption.
Detailed technical explanation
How to think about this question
SR-IOV allows a single physical NIC (PF) to present multiple virtual functions (VFs) directly to VMs, bypassing the hypervisor's virtual switch for near-native performance. However, the PF must remain under the control of the hypervisor's network stack; if the PF is also used for the host management network, enabling SR-IOV can cause the PF driver to reset or reconfigure, breaking management connectivity. In production, best practice is to dedicate a separate physical NIC for management traffic when using SR-IOV on other NICs.
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.
TExam Day Tips
→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 350-401 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Virtual Machines and Hypervisors — This question tests Virtual Machines and Hypervisors — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The physical NIC's PF is also used for the host management network, and SR-IOV configuration disrupted it. — When SR-IOV is enabled on a physical NIC, the Physical Function (PF) is shared between the host management network and the Virtual Functions (VFs). If the PF is used for the host management network, enabling SR-IOV can disrupt the PF's driver or configuration, causing the management network to become unreachable. This is a common misconfiguration where the same NIC is used for both management and SR-IOV VFs.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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