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350-401 Practice Question: Virtualizing its network functions using NFV on a…
A company is virtualizing its network functions using NFV on a KVM-based hypervisor. The design must ensure that the virtual router (CSR1000v) can handle high-throughput traffic with minimal latency. Which architectural consideration is most critical for achieving this goal?
⚠ Common exam trap
Cisco often tests the misconception that simply using a Type 1 hypervisor or avoiding overcommitment is sufficient, but the trap here is that candidates overlook the critical impact of NUMA locality and vCPU pinning on latency-sensitive VNFs, assuming that any virtualization optimization will suffice.
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
✓
Pin the vCPU of the CSR1000v to dedicated physical cores and ensure the VM memory is allocated from the same NUMA node.
Pinning vCPUs to dedicated physical cores and allocating memory from the same NUMA node eliminates cross-NUMA memory access and CPU scheduling contention, which are critical for reducing latency and maximizing throughput in a data-plane-intensive VNF like the CSR1000v. This ensures that the VM's memory accesses are local to the NUMA node where its vCPUs run, avoiding the performance penalty of remote memory access over the QPI/UPI interconnect.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Pin the vCPU of the CSR1000v to dedicated physical cores and ensure the VM memory is allocated from the same NUMA node.
Why this is correct
NFV throughput depends on CPU and memory locality. Pinning vCPUs to dedicated physical cores prevents hypervisor scheduling contention, while sourcing memory from the same NUMA node avoids cross-node QPI/UPI hops that add latency and reduce packet-processing throughput for the CSR1000v.
- ✗
Use a Type 2 hypervisor to allow the VNF to share resources with other VMs more efficiently.
Why it's wrong here
A Type 2 hypervisor runs atop a host OS, adding scheduling and context-switch overhead that raises latency and caps throughput for the CSR1000v. It appeals because resource sharing sounds efficient for consolidating VNFs, but Type 1 bare-metal hypervisors are the correct choice when deterministic packet forwarding is required.
- ✗
Enable overcommitment of CPU resources to maximize the number of VNFs per host.
Why it's wrong here
CPU overcommitment lets the hypervisor time-slice vCPUs, so the CSR1000v stalls when other VMs contend, producing jitter and dropped packets under peak load. It tempts when maximising VNF density per host, but dedicated or pinned cores are required where high throughput and minimal latency are the design goals.
- ✗
Place the CSR1000v on a VMware ESXi host instead of KVM for better performance.
Why it's wrong here
Swapping to ESXi contradicts the stated KVM-based platform and, without SR-IOV or DPDK equivalent, adds no throughput guarantee; the constraint is virtual switching and CPU pinning, not the hypervisor brand. It tempts because ESXi is widely deployed for NFV, but it would be correct only if the design were not already fixed on KVM.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.