- A
Use localized QoS policies on each WAN edge router with CoS markings based on the transport type.
Why wrong: Localized policies are per-device and can lead to inconsistent markings across transports, complicating troubleshooting.
- B
Use a centralized QoS policy that marks traffic with DSCP and applies per-queue shaping on the WAN edge.
Centralized policies ensure consistent DSCP markings across all transports, and per-queue shaping allows prioritization of voice over video.
- C
Use MPLS EXP markings for MPLS transport and IP Precedence for Internet transport.
Why wrong: Using different marking schemes for different transports defeats the purpose of a consistent QoS strategy and increases complexity.
- D
Use NBAR2 to automatically classify traffic and apply markings based on application signatures.
Why wrong: NBAR2 can classify traffic but does not provide a centralized policy; it is a localized feature and may not ensure consistent markings across all routers.
Quick Answer
The answer is a centralized QoS policy that marks traffic with DSCP and applies per-queue shaping on the WAN edge. This is correct because Cisco SD-WAN uses a centralized policy orchestrated by the vSmart controller to enforce consistent DiffServ marking across both MPLS and Internet transports, ensuring that voice traffic (marked with DSCP EF) is placed in a higher-priority queue than video (marked with DSCP AF41), with per-queue shaping guaranteeing that voice is always serviced first. On the ENCOR 350-401 exam, this question tests your understanding of how SD-WAN QoS policy differs from traditional router-based QoS—the key trap is assuming marking happens locally on each edge device, when in fact the vSmart controller pushes a unified policy to maintain consistency across transports. A common memory tip is to remember that in SD-WAN, the control plane (vSmart) dictates the data plane (vEdge/cEdge) marking, so think “centralized brain, distributed brawn.”
CCNP SD-WAN Architecture Practice Question
This 350-401 practice question tests your understanding of sd-wan architecture. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 architect is designing the QoS architecture for a Cisco SD-WAN deployment that carries voice, video, and data traffic across MPLS and Internet transports. The design must use a consistent DiffServ marking strategy across all transports and ensure that voice traffic is prioritized over video. Which QoS policy type and marking approach should the architect use?
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
Use a centralized QoS policy that marks traffic with DSCP and applies per-queue shaping on the WAN edge.
Option B is correct because Cisco SD-WAN uses centralized QoS policies applied via vSmart to ensure consistent DiffServ marking (DSCP) across all transports (MPLS and Internet). Per-queue shaping on the WAN edge router allows voice traffic to be prioritized over video by assigning voice to a higher-priority queue (e.g., queue 4 with DSCP EF) and video to a lower queue (e.g., queue 3 with DSCP AF41), ensuring voice is always serviced first.
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 localized QoS policies on each WAN edge router with CoS markings based on the transport type.
Why it's wrong here
Localized policies are per-device and can lead to inconsistent markings across transports, complicating troubleshooting.
- ✓
Use a centralized QoS policy that marks traffic with DSCP and applies per-queue shaping on the WAN edge.
Why this is correct
Centralized policies ensure consistent DSCP markings across all transports, and per-queue shaping allows prioritization of voice over video.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use MPLS EXP markings for MPLS transport and IP Precedence for Internet transport.
Why it's wrong here
Using different marking schemes for different transports defeats the purpose of a consistent QoS strategy and increases complexity.
- ✗
Use NBAR2 to automatically classify traffic and apply markings based on application signatures.
Why it's wrong here
NBAR2 can classify traffic but does not provide a centralized policy; it is a localized feature and may not ensure consistent markings across all routers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that localized QoS policies are sufficient for multi-transport consistency, but the trap here is that only centralized QoS policies in SD-WAN can enforce uniform DiffServ markings across all transports, while options like NBAR2 or per-transport markings (EXP vs. IP Precedence) fail to meet the requirement for a consistent strategy.
Detailed technical explanation
How to think about this question
In Cisco SD-WAN, centralized QoS policies are defined on vSmart and pushed to WAN edge routers via OMP (Overlay Management Protocol). The policy uses DSCP markings (e.g., EF for voice, AF41 for video) and applies per-queue shaping using the SD-WAN QoS scheduler, which supports up to 8 queues per tunnel. Voice traffic is placed in the highest-priority queue (queue 4) with strict priority scheduling, while video is placed in queue 3 with bandwidth guarantee, ensuring voice is never starved even during congestion.
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.
What to study next
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FAQ
Questions learners often ask
What does this 350-401 question test?
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: Use a centralized QoS policy that marks traffic with DSCP and applies per-queue shaping on the WAN edge. — Option B is correct because Cisco SD-WAN uses centralized QoS policies applied via vSmart to ensure consistent DiffServ marking (DSCP) across all transports (MPLS and Internet). Per-queue shaping on the WAN edge router allows voice traffic to be prioritized over video by assigning voice to a higher-priority queue (e.g., queue 4 with DSCP EF) and video to a lower queue (e.g., queue 3 with DSCP AF41), ensuring voice is always serviced first.
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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Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 24, 2026
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