- A
Configure a vPC domain between the two access switches and use a vPC on the server-facing ports.
Correct because vPC allows both switches to act as a single logical switch for the server, providing active-active links and redundancy.
- B
Enable Spanning Tree Protocol (STP) to block one of the links to prevent loops.
Why wrong: Incorrect because STP would block one link, reducing redundancy and not allowing both links to be active.
- C
Configure an EtherChannel between the server and each access switch individually.
Why wrong: Incorrect because EtherChannel requires all links to terminate on the same switch, not two different switches.
- D
Implement Virtual Switching System (VSS) on the access switches.
Why wrong: Incorrect because VSS is for Catalyst switches, not Nexus; vPC is the Nexus equivalent.
Quick Answer
The answer is to configure a vPC domain between the two access switches and use a vPC on the server-facing ports. This is correct because a Virtual Port Channel (vPC) allows the two separate Nexus 9000 switches to appear as a single logical device to the dual-homed server, enabling both uplinks to remain active simultaneously while preventing Layer 2 loops without relying on Spanning Tree Protocol to block a port. For active-standby NIC teaming, vPC ensures seamless failover: if the active link fails, the standby link immediately takes over traffic forwarding without interruption, as the vPC peer link and keepalive link maintain synchronization between the switches. On the ENCOR 350-401 exam, this scenario tests your understanding of vPC as a loop-free alternative to STP in server access designs—a common trap is thinking PortChannel or STP tuning alone suffices, but vPC uniquely allows both links to be active while providing sub-second failover. Memory tip: think of vPC as "virtual single switch" for the server—both links stay up, no blocking, no loops.
CCNP VLANs and Trunking Practice Question
This 350-401 practice question tests your understanding of vlans and trunking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 network engineer is deploying a new server farm with multiple servers connected to a Cisco Nexus 9000 switch. Each server is dual-homed to two separate access switches for redundancy. The servers are configured with NIC teaming in active-standby mode. The engineer wants to ensure that if the active link fails, traffic continues without interruption. The access switches are connected to each other via a trunk. Which technology should the engineer implement on the access switches to prevent loops and allow both uplinks to be active?
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
Configure a vPC domain between the two access switches and use a vPC on the server-facing ports.
A is correct because a vPC (Virtual Port Channel) allows two access switches to appear as a single logical device to the server, enabling both uplinks to be active simultaneously while preventing loops. This is essential for active-standby NIC teaming, as vPC ensures that if one link fails, the other continues forwarding traffic without requiring STP to block a port, thus providing seamless failover and loop-free operation.
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.
- ✓
Configure a vPC domain between the two access switches and use a vPC on the server-facing ports.
Why this is correct
Correct because vPC allows both switches to act as a single logical switch for the server, providing active-active links and redundancy.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable Spanning Tree Protocol (STP) to block one of the links to prevent loops.
Why it's wrong here
Incorrect because STP would block one link, reducing redundancy and not allowing both links to be active.
- ✗
Configure an EtherChannel between the server and each access switch individually.
Why it's wrong here
Incorrect because EtherChannel requires all links to terminate on the same switch, not two different switches.
- ✗
Implement Virtual Switching System (VSS) on the access switches.
Why it's wrong here
Incorrect because VSS is for Catalyst switches, not Nexus; vPC is the Nexus equivalent.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between vPC (Nexus) and VSS (Catalyst), and candidates may mistakenly choose VSS for Nexus switches, not realizing it is platform-specific.
Detailed technical explanation
How to think about this question
vPC uses a control plane synchronization mechanism via a vPC peer-link (a trunk between the switches) and a vPC keepalive link (typically a separate L3 link) to ensure both switches forward traffic consistently. In active-standby NIC teaming, the server sends traffic only on the active link, but vPC allows the standby link to be immediately usable upon failure because both switches maintain the same MAC address table and forwarding state, eliminating the need for STP reconvergence.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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.
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VLANs and Trunking — study guide chapter
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FAQ
Questions learners often ask
What does this 350-401 question test?
VLANs and Trunking — This question tests VLANs and Trunking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure a vPC domain between the two access switches and use a vPC on the server-facing ports. — A is correct because a vPC (Virtual Port Channel) allows two access switches to appear as a single logical device to the server, enabling both uplinks to be active simultaneously while preventing loops. This is essential for active-standby NIC teaming, as vPC ensures that if one link fails, the other continues forwarding traffic without requiring STP to block a port, thus providing seamless failover and loop-free operation.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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