The correct answer is to use the 'software install add' command to stage the image, then 'activate' and 'commit' with a single reboot. This method minimizes downtime because it separates the upgrade into distinct phases: first staging the new NFVIS software image without disrupting running virtual network functions, then applying the upgrade and committing it in one reboot cycle, which avoids multiple service interruptions. On the ENCOR 350-401 exam, this question tests your understanding of the NFVIS software upgrade method as part of the automation and virtualization domain, often appearing as a scenario where you must choose between a staged single-reboot approach and a disruptive multi-reboot process. A common trap is selecting a method that requires two reboots or forgetting the 'commit' step, which leaves the system in a non-persistent state. Memory tip: think "Add, Activate, Commit—one reboot, no hit."
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.
An engineer is managing a Cisco NFVIS host running multiple virtual network functions (VNFs). The engineer needs to upgrade the NFVIS software to a new version that includes critical security patches. The upgrade process must minimize downtime. Which upgrade method should the engineer use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the 'software install add' command to stage the image, then 'activate' and 'commit' with a single reboot.
Option B is correct because the 'software install add' command stages the new NFVIS image, followed by 'activate' and 'commit' with a single reboot, which minimizes downtime by performing the upgrade in a single reboot cycle. This method is the recommended approach for upgrading NFVIS while preserving existing VNF configurations and minimizing service disruption.
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.
✗
Use the 'patch install' command to apply the upgrade without rebooting.
Why it's wrong here
Incorrect because NFVIS does not support live patching; a reboot is required.
✓
Use the 'software install add' command to stage the image, then 'activate' and 'commit' with a single reboot.
Why this is correct
Correct because this method stages the upgrade and applies it with one reboot, minimizing downtime.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Perform a clean installation of the new NFVIS version and redeploy all VNFs.
Why it's wrong here
Incorrect because this causes maximum downtime and is not the recommended upgrade procedure.
✗
Migrate all VNFs to another NFVIS host, then upgrade the original host.
Why it's wrong here
Incorrect because this is not a built-in upgrade method and requires additional hardware.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that NFVIS upgrades can be applied without a reboot, but the correct method always requires a single reboot to activate the new software version.
Detailed technical explanation
How to think about this question
The NFVIS upgrade process uses a two-step activation and commit mechanism: after staging the image with 'software install add', the 'activate' command prepares the new version for the next boot, and 'commit' makes it permanent after a successful reboot. This approach ensures that if the new version fails to boot, the system can roll back to the previous version automatically, providing a safety net during the upgrade. In real-world scenarios, this method is critical for maintaining service continuity in production environments where VNFs must be available with minimal interruption.
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 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.
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: Use the 'software install add' command to stage the image, then 'activate' and 'commit' with a single reboot. — Option B is correct because the 'software install add' command stages the new NFVIS image, followed by 'activate' and 'commit' with a single reboot, which minimizes downtime by performing the upgrade in a single reboot cycle. This method is the recommended approach for upgrading NFVIS while preserving existing VNF configurations and minimizing service disruption.
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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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