The answer is that the vEdge routers are designed to use only one vSmart controller at a time, with the second serving purely as a standby for redundancy. This is because Cisco SD-WAN implements an active/standby model for vSmart controller redundancy, not load balancing; the vEdge establishes a single control connection to the primary vSmart and will only fail over to the standby if the primary becomes unreachable. On the ENCOR 350-401 exam, this concept tests your understanding of SD-WAN control plane behavior, often appearing as a trap where candidates assume multiple reachable controllers imply simultaneous active use. A common memory tip is to think of vSmart redundancy like a primary and backup router in a traditional HSRP setup—only one is actively directing traffic at any time. Remember: reachable does not mean active; the vEdge holds the standby in reserve until the primary fails.
350-401 SD-WAN Architecture Practice Question
This 350-401 practice question tests your understanding of sd-wan architecture. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 enterprise is deploying Cisco SD-WAN with multiple vSmart controllers for redundancy. The engineer configures the vEdge routers to connect to two vSmart controllers. After deployment, the engineer notices that the vEdge routers are only connected to one vSmart, and the second vSmart is not being used. The vEdge routers show that the second vSmart is reachable. What is the most likely reason for this behavior?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The vEdge routers are designed to use only one vSmart at a time; the second is for redundancy.
In Cisco SD-WAN, vEdge routers are designed to establish a control connection to only one active vSmart controller at a time, even when multiple vSmart controllers are configured for redundancy. The second vSmart serves as a standby; the vEdge will fail over to it only if the primary vSmart becomes unreachable. Since the vEdge shows the second vSmart is reachable but not actively used, this confirms the expected behavior of active/standby redundancy rather than load balancing.
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.
✓
The vEdge routers are designed to use only one vSmart at a time; the second is for redundancy.
Why this is correct
Correct because vEdge routers use a single active vSmart for OMP, and the second is a backup.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The vEdge routers can only connect to one vSmart at a time.
Why it's wrong here
Incorrect because vEdge routers can connect to multiple vSmarts, but only one is active.
✗
The vEdge routers need to be rebooted to establish a connection to the second vSmart.
Why it's wrong here
Incorrect because reboot is not required.
✗
The second vSmart has a different site ID than the first.
Why it's wrong here
Incorrect because site ID does not affect vSmart connectivity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that multiple vSmart controllers are used for load balancing or concurrent connections, when in fact they are strictly for active/standby redundancy, and a vEdge will only ever hold one active control connection at a time.
Detailed technical explanation
How to think about this question
Under the hood, vEdge routers establish a DTLS or TLS control connection to the vSmart with the highest priority (configured via the 'vsmart' list in the vEdge's configuration). The vEdge sends periodic keepalives; if the primary vSmart fails to respond, the vEdge tears down the connection and attempts to connect to the next vSmart in the list. This behavior is defined in the Cisco SD-WAN control plane architecture, where vSmarts act as route reflectors but do not support active-active control connections from a single vEdge.
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 350-401 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
SD-WAN Architecture — This question tests SD-WAN Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The vEdge routers are designed to use only one vSmart at a time; the second is for redundancy. — In Cisco SD-WAN, vEdge routers are designed to establish a control connection to only one active vSmart controller at a time, even when multiple vSmart controllers are configured for redundancy. The second vSmart serves as a standby; the vEdge will fail over to it only if the primary vSmart becomes unreachable. Since the vEdge shows the second vSmart is reachable but not actively used, this confirms the expected behavior of active/standby redundancy rather than load balancing.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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