hardMultiple Choice
350-401 Practice Question: Runs the following command on Router R2: R2# show…
A network engineer runs the following command on Router R2:
R2# show class-map
Class Map match-any VOICE (id 1) Match ip dscp ef (46) Class Map match-any DATA (id 2) Match ip dscp af31 (26) Class Map match-any class-default (id 0) Match any
R2# show policy-map
Policy Map QOS_POLICY Class VOICE priority level 1 police cir 1000000 bc 15625 be 15625 Class DATA bandwidth remaining percent 50 Class class-default bandwidth remaining percent 50
R2# show policy-map interface GigabitEthernet0/1
GigabitEthernet0/1
Service-policy output: QOS_POLICY
Class-map: VOICE (match-any) 0 packets, 0 bytes 5 minute offered rate 0 bps, drop rate 0 bps Match: ip dscp ef (46) Queueing strict priority queue limit 64 packets (queue depth/total drops/no-buffer drops) 0/0/0 (pkts output/bytes output) 0/0 police cir 1000000 bc 15625 be 15625 conformed 0 packets, 0 bytes; actions: transmit exceeded 0 packets, 0 bytes; actions: drop violated 0 packets, 0 bytes; actions: drop
Class-map: DATA (match-any) 0 packets, 0 bytes 5 minute offered rate 0 bps, drop rate 0 bps Match: ip dscp af31 (26) Queueing (queue depth/total drops/no-buffer drops) 0/0/0 (pkts output/bytes output) 0/0 bandwidth remaining percent 50 (0 kbps)
Class-map: class-default (match-any) 100 packets, 10000 bytes 5 minute offered rate 0 bps, drop rate 0 bps Match: any Queueing (queue depth/total drops/no-buffer drops) 0/0/0 (pkts output/bytes output) 100/10000 bandwidth remaining percent 50 (0 kbps)
Based on this output, what can be concluded?
⚠ Common exam trap
Cisco often tests the misconception that simply configuring a QoS policy means it is actively shaping or prioritizing traffic, but the key is to check the actual packet counters to see which classes are receiving traffic.
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
✓
All traffic is being handled by class-default, which gets 100% of the bandwidth.
The output shows that only class-default has processed any packets (100 packets, 10000 bytes), while the VOICE and DATA classes have zero packets. This indicates that no traffic matching DSCP EF or AF31 has been offered, so all traffic falls into class-default, which is allocated 50% of the remaining bandwidth. However, since the VOICE class is empty, the priority queue is unused, and class-default effectively receives all available bandwidth.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Voice traffic is being prioritized with strict priority queuing and policed at 1 Mbps.
Why it's wrong here
The VOICE class in the policy map is configured with strict-priority queuing and a 1 Mbps police rate, but the classification counters show 0 packets matched. An empty priority queue never gets serviced, so no voice traffic is actually being prioritized, and the policer never sees a packet to evaluate. Thus, neither the priority nor the police command has any operational effect on the traffic flow.
- ✗
Data traffic is being guaranteed 50% of the remaining bandwidth.
Why it's wrong here
The DATA class is defined to guarantee 50% of the remaining bandwidth, but the packet counters indicate 0 packets have been classified into that class. A CBWFQ bandwidth command reserves a minimum amount of bandwidth for a class only when there are queued packets in that class; with an empty queue, the reserved 50% is simply left unused. Consequently, the guarantee is not 'being applied' — class-default borrows the entire bandwidth because no data packets exist to consume the reservation.
- ✓
All traffic is being handled by class-default, which gets 100% of the bandwidth.
Why this is correct
The policy-map output shows that only class-default has matched traffic, with 100 packets. On Cisco IOS, class-default is the implicit final class that catches all packets not matched by user-defined class-maps; when it is the only class with non-zero traffic, it is allowed to use 100% of the interface bandwidth. Since VOICE and DATA classes are empty, no other queuing or policing actions are invoked, and class-default receives the full link capacity.
- ✗
The police command on VOICE is causing drops for voice traffic.
Why it's wrong here
The police command on the VOICE class can only cause drops for packets that actually match the class's match criteria. The show policy-map counters reveal 0 packets in the VOICE class, meaning the policer has never evaluated a frame. Therefore, no voice packets are being dropped — the drop counter for the VOICE policer remains zero, and the police command is not contributing to any packet loss.
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