The answer is to configure CPU pinning and use dedicated NUMA nodes. This is correct because CPU pinning binds the VNF’s virtual CPUs to specific physical cores, guaranteeing dedicated compute resources and eliminating performance interference from other VMs on the KVM host. Adding dedicated NUMA nodes further optimizes memory locality, ensuring that the VNF’s memory accesses stay within the same physical processor socket, which avoids costly cross-NUMA memory traffic and reduces latency—critical for performance-sensitive VNFs. On the ENCOR 350-401 exam, this scenario tests your understanding of how virtualization features like CPU pinning and NUMA awareness directly impact network function performance; a common trap is assuming that simply reserving CPU resources is enough, but without pinning and NUMA alignment, the hypervisor can still migrate vCPUs or use remote memory, degrading throughput. Remember the mnemonic “Pin and Bind, Keep Memory Kind”—pinning locks cores, and NUMA keeps memory local.
350-401 Network Function Virtualization Practice Question
This 350-401 practice question tests your understanding of network function virtualization. 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 network function (VNF) on a KVM-based host. The VNF requires dedicated CPU cores and must avoid performance interference from other VMs. Which hypervisor configuration best meets these requirements?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure CPU pinning and use dedicated NUMA nodes.
Option B is correct because CPU pinning binds the VNF's vCPUs to specific physical cores, ensuring dedicated CPU resources and preventing interference from other VMs. Using dedicated NUMA nodes further optimizes memory locality, reducing latency and avoiding cross-NUMA memory access, which is critical for performance-sensitive VNFs.
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.
✗
Enable CPU overcommitment and use a single NUMA node.
Why it's wrong here
CPU overcommitment increases contention, which is undesirable for VNF performance.
✓
Configure CPU pinning and use dedicated NUMA nodes.
Why this is correct
CPU pinning and dedicated NUMA nodes minimize interference and improve performance.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use VMware vSphere with DRS set to Aggressive.
Why it's wrong here
DRS dynamically balances load, which can cause VM migration and performance variation.
✗
Deploy the VNF as a container instead of a VM.
Why it's wrong here
Containers share the host kernel and may not provide the same level of isolation as pinned VMs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between hypervisor-agnostic concepts (like CPU pinning) and vendor-specific features (like VMware DRS), and the trap here is that candidates may choose VMware options even when the question explicitly specifies a KVM-based host.
Detailed technical explanation
How to think about this question
CPU pinning is implemented in KVM using the `virsh vcpupin` command or via libvirt domain XML with `<vcpupin>` elements, which map vCPUs to specific host pCPUs. Dedicated NUMA nodes are configured by assigning the VM to a specific NUMA node using `<numatune>` and `<memnode>` elements, ensuring memory is allocated from the same node as the pinned CPUs, which avoids remote memory access penalties. In real-world NFV deployments, this is essential for achieving deterministic performance in DPDK-based VNFs that rely on poll-mode drivers and require low-latency packet processing.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Network Function Virtualization — This question tests Network Function Virtualization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure CPU pinning and use dedicated NUMA nodes. — Option B is correct because CPU pinning binds the VNF's vCPUs to specific physical cores, ensuring dedicated CPU resources and preventing interference from other VMs. Using dedicated NUMA nodes further optimizes memory locality, reducing latency and avoiding cross-NUMA memory access, which is critical for performance-sensitive VNFs.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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