350-501 Automation and Quality of Service Practice Question
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 bpsRefer 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?
⚠ Common exam trap
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.
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 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.
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.
- ✗
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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