350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. 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.
Exhibit
router# show policy-map interface GigabitEthernet0/0/0
GigabitEthernet0/0/0
Service-policy input: QOS_INPUT
Class-map: VOICE (match-any)
9286 packets, 12345678 bytes
5 minute offered rate 100000 bps, drop rate 0 bps
Match: ip dscp ef (46)
police:
cir 64000 bps, bc 8000 bytes
conformed 5000 packets, 6400000 bytes; actions:
set-dscp-transmit ef
exceeded 4286 packets, 5934578 bytes; actions:
drop
conformed 60000 bps, exceed 40000 bps
Class-map: DATA (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp af31 (26)
Class-map: class-default
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Refer to the exhibit. The policy above is applied on a PE router. The customer complains that voice quality is poor. Based on the exhibit, 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.
router# show policy-map interface GigabitEthernet0/0/0
GigabitEthernet0/0/0
Service-policy input: QOS_INPUT
Class-map: VOICE (match-any)
9286 packets, 12345678 bytes
5 minute offered rate 100000 bps, drop rate 0 bps
Match: ip dscp ef (46)
police:
cir 64000 bps, bc 8000 bytes
conformed 5000 packets, 6400000 bytes; actions:
set-dscp-transmit ef
exceeded 4286 packets, 5934578 bytes; actions:
drop
conformed 60000 bps, exceed 40000 bps
Class-map: DATA (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp af31 (26)
Class-map: class-default
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
A
The police rate for voice is too low for the offered traffic
The offered rate of 100 kbps exceeds the policed rate of 64 kbps, causing significant drops (over 40% of packets dropped), which directly impacts voice quality.
B
The policy is applied to the wrong direction
Why wrong: The policy is applied inbound, which is correct for classifying and policing incoming traffic.
C
The class-default is empty
Why wrong: An empty class-default does not affect voice performance; it simply means no other traffic is present.
D
The DATA class is not matching any traffic
Why wrong: The DATA class not matching traffic is unrelated to the voice issue; it may be a separate problem.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The police rate for voice is too low for the offered traffic
The police rate for voice is too low for the offered traffic. Voice traffic requires a guaranteed bandwidth to maintain low jitter and packet loss; if the policer rate is set below the actual voice flow rate, packets are dropped or marked down, causing poor voice quality. In the exhibit, the voice class has a police rate that is insufficient for the offered load, leading to excessive drops.
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 police rate for voice is too low for the offered traffic
Why this is correct
The offered rate of 100 kbps exceeds the policed rate of 64 kbps, causing significant drops (over 40% of packets dropped), which directly impacts voice quality.
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 policy is applied to the wrong direction
Why it's wrong here
The policy is applied inbound, which is correct for classifying and policing incoming traffic.
✗
The class-default is empty
Why it's wrong here
An empty class-default does not affect voice performance; it simply means no other traffic is present.
✗
The DATA class is not matching any traffic
Why it's wrong here
The DATA class not matching traffic is unrelated to the voice issue; it may be a separate problem.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that applying a policy in the correct direction is sufficient, but the trap here is that the police rate itself must be properly sized for the actual voice traffic load, not just the classification.
Detailed technical explanation
How to think about this question
Policing uses a token bucket algorithm to enforce a committed information rate (CIR) and burst size; when the offered rate exceeds the CIR, packets are either dropped or marked with a lower IP precedence/CoS value. For real-time traffic like VoIP (typically G.711 at 64 kbps per call plus overhead), the policer must account for Layer 2 headers and RTP/UDP/IP overhead, often requiring a rate of 80-100 kbps per call. If the police rate is set too low, even momentary bursts cause drops, degrading Mean Opinion Score (MOS) below acceptable thresholds.
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 rate for voice is too low for the offered traffic — The police rate for voice is too low for the offered traffic. Voice traffic requires a guaranteed bandwidth to maintain low jitter and packet loss; if the policer rate is set below the actual voice flow rate, packets are dropped or marked down, causing poor voice quality. In the exhibit, the voice class has a police rate that is insufficient for the offered load, leading to excessive drops.
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.
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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