- A
The shaper should be applied to the physical interface instead of the tunnel interface
Correct because tunnel interfaces encapsulate traffic; shaping on the tunnel does not control the actual output rate on the physical link.
- B
The shaper rate should be set to 20 Mbps to match the tunnel bandwidth
Why wrong: Incorrect because increasing the shaper rate would allow even more traffic, not solve the problem of shaping not working.
- C
The class map should match on the outer IP header instead of the inner DSCP
Why wrong: Incorrect because the inner DSCP is preserved in the tunnel; matching on the outer header would not match the original DSCP.
- D
The service policy should be applied in the input direction
Why wrong: Incorrect because shaping is only supported on output policies; input direction does not shape.
Quick Answer
The answer is that the shaper must be applied to the physical interface, not the tunnel interface. This is because a tunnel interface encapsulates traffic and has no direct awareness of the underlying physical link’s bandwidth or queuing mechanisms; shaping on a tunnel interface simply queues packets before encapsulation, but the actual transmission rate is still governed by the physical egress interface. On the ENCOR 350-401 exam, this scenario tests your understanding of QoS hierarchy and the fact that tunnel interfaces are logical constructs—applying a shaper there is ineffective because the physical interface controls the true egress rate. A common trap is assuming the shaper on the tunnel will throttle traffic, but it only adds overhead without limiting throughput. Remember the memory tip: “Shape where the wire lives”—always apply shaping to the physical interface that owns the bandwidth.
350-401 QoS Practice Question
This 350-401 practice question tests your understanding of qos. 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.
An engineer is configuring QoS on a Cisco ISR 4331 router for a site-to-site VPN tunnel. The tunnel interface is configured with a service policy that uses a class map matching DSCP EF. The engineer notices that the policy is not shaping traffic as expected; the tunnel bandwidth is 20 Mbps but the shaper is set to 10 Mbps. However, traffic still exceeds 10 Mbps. What is the most likely cause?
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 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
The shaper should be applied to the physical interface instead of the tunnel interface
The correct answer is that the shaper must be applied to the physical interface, not the tunnel interface, because the tunnel interface does not have a direct view of the underlying bandwidth. Shaping on the tunnel interface is ineffective.
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 shaper should be applied to the physical interface instead of the tunnel interface
Why this is correct
Correct because tunnel interfaces encapsulate traffic; shaping on the tunnel does not control the actual output rate on the physical link.
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 shaper rate should be set to 20 Mbps to match the tunnel bandwidth
Why it's wrong here
Incorrect because increasing the shaper rate would allow even more traffic, not solve the problem of shaping not working.
- ✗
The class map should match on the outer IP header instead of the inner DSCP
Why it's wrong here
Incorrect because the inner DSCP is preserved in the tunnel; matching on the outer header would not match the original DSCP.
- ✗
The service policy should be applied in the input direction
Why it's wrong here
Incorrect because shaping is only supported on output policies; input direction does not shape.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
Incorrect because shaping is only supported on output policies; input direction does not shape.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
- →
QoS — study guide chapter
Learn the concepts, then practise the questions
- →
QoS practice questions
Targeted practice on this topic area only
- →
All 350-401 questions
2,015 questions across all exam domains
- →
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
- →
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 350-401 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Architecture practice questions
Practise 350-401 questions linked to Architecture.
Enterprise Network Design practice questions
Practise 350-401 questions linked to Enterprise Network Design.
SD-Access Architecture practice questions
Practise 350-401 questions linked to SD-Access Architecture.
SD-WAN Architecture practice questions
Practise 350-401 questions linked to SD-WAN Architecture.
QoS Architecture practice questions
Practise 350-401 questions linked to QoS Architecture.
Virtualization practice questions
Practise 350-401 questions linked to Virtualization.
Network Function Virtualization practice questions
Practise 350-401 questions linked to Network Function Virtualization.
Virtual Machines and Hypervisors practice questions
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
VRF and Path Isolation practice questions
Practise 350-401 questions linked to VRF and Path Isolation.
Infrastructure practice questions
Practise 350-401 questions linked to Infrastructure.
OSPF practice questions
Practise 350-401 questions linked to OSPF.
BGP practice questions
Practise 350-401 questions linked to BGP.
Practice this exam
Start a free 350-401 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 350-401 question test?
QoS — This question tests QoS — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The shaper should be applied to the physical interface instead of the tunnel interface — The correct answer is that the shaper must be applied to the physical interface, not the tunnel interface, because the tunnel interface does not have a direct view of the underlying bandwidth. Shaping on the tunnel interface is ineffective.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
About these practice questions
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 →
Keep practising
More 350-401 practice questions
- Drag and drop the steps to configure an extended access control list (ACL) on a Cisco router in the correct order.
- Drag and drop the steps to configure a site-to-site IPsec VPN on a Cisco router in the correct order.
- Drag and drop the steps to configure VLAN Trunking Protocol (VTP) on a Cisco switch in the correct order.
- Drag and drop the steps to configure a static route on a Cisco IOS router into the correct order.
- Drag and drop the steps to configure port security on a Cisco switch in the correct order.
- Drag and drop the steps for the Spanning Tree Protocol (STP) convergence process in the correct order.
Last reviewed: Jun 18, 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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.