Question 1,503 of 2,015

Network Function Virtualization →mediumMultiple SelectObjective-mapped

Quick Answer

The correct answer is that DPDK provides a set of libraries and drivers for fast packet processing in user space, bypassing the kernel network stack, while SR-IOV allows a physical NIC to be directly assigned to a VM for near-native performance. These two techniques are the primary software and hardware methods for NFV performance acceleration, as SR-IOV eliminates hypervisor virtual switch overhead by giving the VM direct hardware access, and DPDK moves packet processing out of the kernel into user space to avoid costly context switches. On the ENCOR 350-401 exam, this topic tests your understanding of how to optimize virtualized network functions without relying on dedicated hardware, often appearing as a choose-two question where common traps include confusing NUMA awareness or vSwitch bonding as primary acceleration methods. Remember the memory tip: “SR-IOV gives the NIC directly to the VM, DPDK gives packets a fast lane in user space.”

CCNP Network Function Virtualization Practice Question

This 350-401 practice question tests your understanding of network function virtualization. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.

Which two statements about NFV performance considerations are true? (Choose two.)

Question 1mediummulti select

Study the full virtualization explanation →

A
SR-IOV allows a virtual function (VF) to be directly assigned to a VM, providing near-native network performance.
Correct because SR-IOV enables direct assignment of PCIe functions to VMs, bypassing the hypervisor virtual switch and reducing latency.
B
NUMA awareness is the primary technique to improve NFV packet processing performance.
Why wrong: Incorrect while NUMA awareness is important for memory locality, it is not the primary technique; SR-IOV and DPDK are more directly focused on packet processing acceleration.
C
DPDK provides a set of libraries and drivers for fast packet processing in user space, bypassing the kernel network stack.
Correct because DPDK allows applications to process packets directly from the NIC in user space, significantly improving throughput and reducing latency.
D
Using a virtual switch with multiple bonded uplinks eliminates the need for any performance optimization.
Why wrong: Incorrect because bonding uplinks provides redundancy and load balancing but does not eliminate the overhead of the virtual switch; performance optimizations are still required.
E
NFV performance is inherently lower than physical appliances and cannot be improved.
Why wrong: Incorrect because NFV performance can be optimized using techniques like SR-IOV, DPDK, and CPU pinning to approach or even match physical appliance performance in many scenarios.

Full breakdown with real-world context →

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

✓

SR-IOV allows a virtual function (VF) to be directly assigned to a VM, providing near-native network performance.

NFV performance can be improved using various acceleration techniques. Single Root I/O Virtualization (SR-IOV) allows a physical NIC to be directly assigned to a VM, bypassing the hypervisor's virtual switch for better performance. Data Plane Development Kit (DPDK) provides a set of libraries for fast packet processing in user space. Option A is correct because SR-IOV provides near-native performance. Option C is correct because DPDK accelerates packet processing. Option B is incorrect because NUMA awareness helps but is not the primary technique. Option D is incorrect because vSwitch bonding does not eliminate the vSwitch overhead. Option E is incorrect because NFV performance can be optimized with software techniques.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
SR-IOV allows a virtual function (VF) to be directly assigned to a VM, providing near-native network performance.
Why this is correct
Correct because SR-IOV enables direct assignment of PCIe functions to VMs, bypassing the hypervisor virtual switch and reducing latency.
Related concept
Static NAT maps one inside address to one outside address.
✗
NUMA awareness is the primary technique to improve NFV packet processing performance.
Why it's wrong here
Incorrect while NUMA awareness is important for memory locality, it is not the primary technique; SR-IOV and DPDK are more directly focused on packet processing acceleration.
✓
DPDK provides a set of libraries and drivers for fast packet processing in user space, bypassing the kernel network stack.
Why this is correct
Correct because DPDK allows applications to process packets directly from the NIC in user space, significantly improving throughput and reducing latency.
Related concept
Static NAT maps one inside address to one outside address.
✗
Using a virtual switch with multiple bonded uplinks eliminates the need for any performance optimization.
Why it's wrong here
Incorrect because bonding uplinks provides redundancy and load balancing but does not eliminate the overhead of the virtual switch; performance optimizations are still required.
✗
NFV performance is inherently lower than physical appliances and cannot be improved.
Why it's wrong here
Incorrect because NFV performance can be optimized using techniques like SR-IOV, DPDK, and CPU pinning to approach or even match physical appliance performance in many scenarios.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Trap categories for this question

Scenario analysis trap
Incorrect because NFV performance can be optimized using techniques like SR-IOV, DPDK, and CPU pinning to approach or even match physical appliance performance in many scenarios.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Real-world example

How this comes up in practice

A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.

What to study next

Got this wrong? Here's your next step.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this 350-401 question test?

Network Function Virtualization — This question tests Network Function Virtualization — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: SR-IOV allows a virtual function (VF) to be directly assigned to a VM, providing near-native network performance. — NFV performance can be improved using various acceleration techniques. Single Root I/O Virtualization (SR-IOV) allows a physical NIC to be directly assigned to a VM, bypassing the hypervisor's virtual switch for better performance. Data Plane Development Kit (DPDK) provides a set of libraries for fast packet processing in user space. Option A is correct because SR-IOV provides near-native performance. Option C is correct because DPDK accelerates packet processing. Option B is incorrect because NUMA awareness helps but is not the primary technique. Option D is incorrect because vSwitch bonding does not eliminate the vSwitch overhead. Option E is incorrect because NFV performance can be optimized with software techniques.

What should I do if I get this 350-401 question wrong?

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

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