The answer is that the police command is missing an exceed-action, so traffic is transmitted instead of dropped. In Cisco IOS QoS, the `police` command enforces a committed information rate (CIR), but without an explicit `exceed-action`—such as `drop` or `set-dscp-transmit`—the router defaults to transmitting all excess traffic, effectively rendering the policer inactive. This is why policing appears not to drop packets even when the rate surpasses 1 Mbps. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this concept frequently appears as a common trap: candidates assume a policer automatically drops excess traffic, but the default behavior is to forward it. The exam tests your understanding that policing requires a defined action for both conforming and exceeding traffic. A helpful memory tip is “no exceed-action means no teeth”—without specifying what to do with excess, the policer cannot enforce a drop.
350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. 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.
Exhibit
interface GigabitEthernet0/0/0
service-policy input POLICE_IN
service-policy output SHAPE_OUT
!
policy-map POLICE_IN
class VOICE
police cir 1000000
!
policy-map SHAPE_OUT
class class-default
shape average 10000000
Refer to the exhibit. An engineer checks the policy and notices that the policing is not working as expected—traffic is not being dropped even when exceeding 1 Mbps. What could be the issue?
interface GigabitEthernet0/0/0
service-policy input POLICE_IN
service-policy output SHAPE_OUT
!
policy-map POLICE_IN
class VOICE
police cir 1000000
!
policy-map SHAPE_OUT
class class-default
shape average 10000000
A
The service-policy is applied inbound, but police should be applied outbound to be effective
Why wrong: Policing can be applied in either direction; inbound policing is valid and commonly used.
B
The police command is missing an exceed-action, so traffic is transmitted instead of dropped
Without an explicit exceed-action, Cisco IOS defaults to 'transmit' for conforming and exceeding traffic, meaning no packets are dropped.
C
The police rate is too high compared to interface speed
Why wrong: The interface speed is gigabit, so a 1 Mbps police rate is low; drops should occur if traffic exceeds it, but the lack of drop action is the real issue.
D
The shape command is interfering with the police command
Why wrong: Shape and police are applied on different directions; they do not interfere with each other.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The police command is missing an exceed-action, so traffic is transmitted instead of dropped
Option B is correct because the `police` command in Cisco IOS QoS requires an explicit `exceed-action` to define what happens to traffic that exceeds the committed information rate (CIR). Without specifying an action like `drop`, the default behavior is to transmit the excess traffic, which explains why no packets are being dropped even when the rate exceeds 1 Mbps. The policing logic is still applied, but without an exceed-action, the router simply forwards all traffic, rendering the policer 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 service-policy is applied inbound, but police should be applied outbound to be effective
Why it's wrong here
Policing can be applied in either direction; inbound policing is valid and commonly used.
✓
The police command is missing an exceed-action, so traffic is transmitted instead of dropped
Why this is correct
Without an explicit exceed-action, Cisco IOS defaults to 'transmit' for conforming and exceeding traffic, meaning no packets are dropped.
Related concept
Read the scenario before looking for a memorised answer.
✗
The police rate is too high compared to interface speed
Why it's wrong here
The interface speed is gigabit, so a 1 Mbps police rate is low; drops should occur if traffic exceeds it, but the lack of drop action is the real issue.
✗
The shape command is interfering with the police command
Why it's wrong here
Shape and police are applied on different directions; they do not interfere with each other.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the default behavior of the `police` command, specifically that without an `exceed-action`, traffic is transmitted rather than dropped, which catches candidates who assume policing always drops excess traffic.
Detailed technical explanation
How to think about this question
Under the hood, the `police` command uses a token bucket algorithm to meter traffic. When no `exceed-action` is configured, the default behavior is `transmit`, meaning all packets are forwarded regardless of the token bucket state. This is a common misconfiguration because engineers often assume that a policer will automatically drop excess traffic, but Cisco IOS requires an explicit action for both conform and exceed conditions. In real-world scenarios, this mistake can lead to silent SLA violations where traffic bursts are not controlled as intended.
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 350-501 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Automation and Quality of Service — This question tests Automation and Quality of Service — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The police command is missing an exceed-action, so traffic is transmitted instead of dropped — Option B is correct because the `police` command in Cisco IOS QoS requires an explicit `exceed-action` to define what happens to traffic that exceeds the committed information rate (CIR). Without specifying an action like `drop`, the default behavior is to transmit the excess traffic, which explains why no packets are being dropped even when the rate exceeds 1 Mbps. The policing logic is still applied, but without an exceed-action, the router simply forwards all traffic, rendering the policer ineffective.
What should I do if I get this 350-501 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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