The answer is that the hub site is not configured with a different site ID than the branches. In Cisco SD-WAN, a centralized control policy that sets a preferred path for routes only influences OMP route preference, but it cannot override the fundamental behavior that vEdge routers will establish direct branch-to-branch tunnels when they share the same site ID as the hub. Without a distinct site ID for the hub, the TLOC resolution logic treats the hub as part of the same site, allowing direct traffic instead of forcing it through the hub for security inspection. This question tests your understanding of how site IDs govern tunnel creation and policy enforcement in SD-WAN hub-and-spoke designs, a common trap on the ENCOR 350-401 exam where candidates assume a control policy alone can force traffic flow. Remember: the policy steers routes, but the site ID steers tunnels—if the hub’s site ID matches the branches, direct paths win. A useful mnemonic is “Same ID, direct ride; different ID, hub inside.”
350-401 SD-WAN Architecture Practice Question
This 350-401 practice question tests your understanding of sd-wan architecture. 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.
An enterprise is deploying Cisco SD-WAN with a hub-and-spoke topology. The hub site has a vSmart controller and a vEdge router. The branch sites have vEdge routers. The engineer wants to ensure that all inter-branch traffic goes through the hub for security inspection. The engineer configures a centralized control policy on the vSmart to set the 'hub' as the preferred path for all routes. After the policy is applied, the engineer notices that branch-to-branch traffic is still going directly, bypassing the hub. The vEdge routers show that the control policy is received. What is the most likely issue?
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 hub site is not configured with a different site ID than the branches.
In Cisco SD-WAN, a centralized control policy that sets a preferred path for routes only influences route preference within the OMP routing table. However, for branch-to-branch traffic to be forced through the hub, the hub must have a different site ID than the branches. Without a distinct site ID, the vEdge routers treat the hub as part of the same site and will attempt direct branch-to-branch tunnels (using TLOC resolution) instead of routing through the hub. The control policy is received but cannot override the default behavior of same-site direct connectivity.
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 control policy is not attached to the correct site list.
Why it's wrong here
Incorrect because the engineer verified the policy is received, but the topology configuration is the issue.
✓
The hub site is not configured with a different site ID than the branches.
Why this is correct
Correct because the hub must have a unique site ID to be recognized as the hub in the topology.
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 engineer should have used a data policy instead of a control policy.
Why it's wrong here
Incorrect because a control policy is the correct method to influence route advertisement for hub-and-spoke.
✗
The OMP admin distance is set too high on the hub.
Why it's wrong here
Incorrect because OMP admin distance does not affect policy application.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between control policy affecting route preference and site ID affecting tunnel establishment, leading candidates to overlook the mandatory requirement for different site IDs in hub-and-spoke topologies.
Detailed technical explanation
How to think about this question
In Cisco SD-WAN, the site ID is a fundamental construct that determines whether vEdge routers establish direct IPsec tunnels (same site ID) or route through a hub (different site ID). When all sites share the same site ID, the vEdge routers use TLOC resolution to create direct transport tunnels between branches, bypassing any hub-based routing policies. The control policy sets route preferences in OMP, but the actual forwarding decision is made based on the TLOC and tunnel resolution, which is driven by site ID configuration.
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.
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 hub site is not configured with a different site ID than the branches. — In Cisco SD-WAN, a centralized control policy that sets a preferred path for routes only influences route preference within the OMP routing table. However, for branch-to-branch traffic to be forced through the hub, the hub must have a different site ID than the branches. Without a distinct site ID, the vEdge routers treat the hub as part of the same site and will attempt direct branch-to-branch tunnels (using TLOC resolution) instead of routing through the hub. The control policy is received but cannot override the default behavior of same-site direct connectivity.
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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