ACSP Quality of Service (QoS) 4 — Questions and Answers
Question 1: In Aruba AOS-CX, which command verifies the current QoS schedule profile applied to a specific interface?
- show qos interface <port> (Correct answer)
- show interface <port> qos
- show qos schedule-profile applied
- show run interface <port>
Correct answer: show qos interface <port>
'show qos interface <port>' displays the QoS settings, queue statistics, and schedule profile currently active on the specified interface.
Question 2: What is the default DSCP value assigned to traffic on an Aruba switch port that has no QoS trust or remarking configured?
- DSCP 46
- DSCP 48
- DSCP 0 (Correct answer)
- DSCP 16
Correct answer: DSCP 0
Without explicit QoS configuration, traffic is treated as best-effort with DSCP 0 (CS0), placing it in the lowest-priority queue.
Question 3: Which QoS scheduling combination on Aruba switches provides the highest determinism for real-time traffic while still serving lower-priority queues?
- All queues using WRR
- One strict-priority queue for real-time traffic with WRR for remaining queues (Correct answer)
- All queues using strict priority
- FIFO for all queues with policing at ingress
Correct answer: One strict-priority queue for real-time traffic with WRR for remaining queues
Using one strict queue for real-time traffic (voice/video) combined with WRR for other queues ensures low latency for critical traffic while preventing starvation of lower queues.
Question 4: On an Aruba switch, 'burst size' in a traffic policer configuration refers to what?
- The maximum queue depth before tail drop activates
- The maximum number of bytes allowed to exceed the committed rate instantaneously (Correct answer)
- The minimum guaranteed bandwidth for the flow
- The interval between token bucket refills
Correct answer: The maximum number of bytes allowed to exceed the committed rate instantaneously
Burst size (Bc) defines how many bytes above the committed rate a flow can send instantaneously before packets are dropped or remarked.
Question 5: Which DSCP per-hop behavior class is designed for network control traffic such as OSPF and BGP on Aruba switches?
- Assured Forwarding (AF)
- Expedited Forwarding (EF)
- Class Selector 6 (CS6) (Correct answer)
- Default Forwarding (DF)
Correct answer: Class Selector 6 (CS6)
CS6 (DSCP 48) is conventionally used for network control plane traffic like routing protocols, ensuring it receives high-priority treatment.
Question 6: An Aruba switch administrator wants to limit a specific application's bandwidth to 10 Mbps and remarked excess traffic rather than drop it. Which policer action should be configured?
- action exceed drop
- action exceed remark dscp <value> (Correct answer)
- action exceed queue lowest
- action exceed shape 10m
Correct answer: action exceed remark dscp <value>
The 'action exceed remark dscp' option allows traffic above the committed rate to be forwarded with a lower DSCP value instead of being dropped.
Question 7: Which Aruba AOS-CX feature can automatically detect and prioritize Microsoft Teams or Zoom traffic without requiring manual DSCP classification?
- Application-aware QoS using NBAR (Correct answer)
- DSCP pass-through mode
- Link Aggregation QoS hash
- STP port cost-based QoS
Correct answer: Application-aware QoS using NBAR
Application-aware QoS using NBAR (Network Based Application Recognition) can identify application flows by deep packet inspection and apply appropriate QoS policies automatically.
ACSP Quality of Service (QoS) 4
In Aruba AOS-CX, which command verifies the current QoS schedule profile applied to a specific interface?