The correct answer is to upgrade the secondary vPC peer first, then the primary. This sequence minimizes traffic disruption because the primary peer remains the forwarding anchor throughout the process; when the secondary peer reboots, the primary continues to handle all data-plane traffic without interruption. Once the secondary rejoins the vPC domain and is stable, the primary can be upgraded, ensuring that at least one peer is always forwarding. On the Cisco DCCOR / CCNP Data Center Core 350-601 exam, this concept tests your understanding of vPC role preservation and graceful upgrade procedures—a common trap is assuming you should upgrade the primary first to “get it over with,” which would cause a traffic outage. Remember the memory tip: “Second goes first, primary stays last.”
350-601 Network Practice Question
This 350-601 practice question tests your understanding of network. 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.
During a maintenance window, a network engineer plans to upgrade the NX-OS software on a pair of Nexus 9000 switches configured as vPC peers. The engineer wants to minimize traffic disruption. Which upgrade sequence is recommended?
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
✓
Upgrade the secondary vPC peer first, then the primary
In a vPC pair, the secondary peer is upgraded first to preserve the primary's role as the forwarding anchor. Upgrading the secondary peer allows it to reboot and rejoin the vPC domain without disrupting the data plane because the primary peer continues to forward traffic. Once the secondary is stable, the primary is upgraded, ensuring minimal traffic loss.
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.
✗
Upgrade both switches simultaneously using ISSU
Why it's wrong here
Issuing ISSU on both at the same time can cause vPC inconsistencies and potential traffic loss; it is not recommended.
✗
Reload both switches to a previous version, then upgrade
Why it's wrong here
Reloading to a previous version adds unnecessary disruption; the goal is to upgrade with minimal impact.
✗
Upgrade the primary vPC peer first, then the secondary
Why it's wrong here
Upgrading primary first can cause role instability; best practice is to upgrade secondary first.
✓
Upgrade the secondary vPC peer first, then the primary
Why this is correct
Upgrading secondary first ensures the primary remains operational; after secondary upgrade, it can take over if needed during primary upgrade.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that upgrading the primary first is safer because it is the 'leader,' but the correct sequence is to upgrade the secondary first to avoid a disruptive role transition.
Detailed technical explanation
How to think about this question
During a vPC upgrade, the secondary peer is upgraded first to maintain the primary's forwarding state. After the secondary reboots, it synchronizes its configuration and state via the vPC peer-keepalive link and peer-link. The primary is then upgraded, and the secondary temporarily assumes the primary role, ensuring no traffic loss. This sequence is documented in Cisco's vPC upgrade guidelines and is critical for maintaining non-stop forwarding.
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 350-601 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.
Network — This question tests Network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Upgrade the secondary vPC peer first, then the primary — In a vPC pair, the secondary peer is upgraded first to preserve the primary's role as the forwarding anchor. Upgrading the secondary peer allows it to reboot and rejoin the vPC domain without disrupting the data plane because the primary peer continues to forward traffic. Once the secondary is stable, the primary is upgraded, ensuring minimal traffic loss.
What should I do if I get this 350-601 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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Question Discussion
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