QoS

A network engineer is configuring QoS on a Cisco Catalyst 3850 switch to prioritize voice traffic. The switch is connected to an IP phone and a PC using a single access port. The engineer applies a service policy on the access port that marks CoS 5 for voice and CoS 0 for data. However, the IP phone is not receiving any voice packets. What is the most likely cause?

An engineer is deploying QoS on a WAN link between two sites using a Cisco ISR 4451 router. The link is a 10 Mbps MPLS circuit. The engineer wants to ensure that voice traffic (EF) is never dropped, even during congestion. The current policy uses a single class map for voice with a policer that drops excess traffic. During peak hours, users report choppy voice calls. What change should the engineer make?

A network engineer is troubleshooting QoS on a Cisco Nexus 9000 switch. The switch is configured with a policy map that uses a class-default with a bandwidth remaining percent of 100. However, during congestion, traffic in a priority queue (class-map for EF) is experiencing drops even though the priority queue is not fully utilized. What is the most likely cause?

An engineer is configuring QoS on a Cisco ASR 1000 router to support three traffic classes: voice (EF), video (AF41), and data (default). The link is a 50 Mbps Ethernet circuit. The engineer wants to guarantee 10 Mbps for voice, 20 Mbps for video, and the remaining for data. The current policy uses bandwidth percent statements. During congestion, voice traffic is not receiving its guaranteed bandwidth. What is the most likely cause?

A network engineer is troubleshooting voice quality issues on a Cisco Catalyst 9300 switch. The switch is configured with auto QoS for voice, which enabled trust on the access ports. However, voice packets are being marked with DSCP EF but are still experiencing jitter. The engineer checks the interface queue statistics and sees that the priority queue is not being used. What is the most likely reason?

An engineer is configuring QoS on a Cisco ISR 4331 router for a site-to-site VPN tunnel. The tunnel interface is configured with a service policy that uses a class map matching DSCP EF. The engineer notices that the policy is not shaping traffic as expected; the tunnel bandwidth is 20 Mbps but the shaper is set to 10 Mbps. However, traffic still exceeds 10 Mbps. What is the most likely cause?

A network engineer is deploying QoS on a Cisco Catalyst 4500 switch to support four queues per port. The engineer wants to assign voice traffic to queue 1 (priority), video to queue 2, critical data to queue 3, and best-effort to queue 4. The switch is configured with the default CoS-to-queue mapping. However, video traffic is being placed in queue 1 along with voice. What should the engineer do to separate them?

An engineer is troubleshooting QoS on a Cisco ASR 1002 router. The router is configured with a policy map that includes a class for voice with a priority command. During congestion, the engineer notices that voice traffic is being dropped even though the priority queue is not congested. The router logs show 'QoS: priority queue overflow'. What is the most likely cause?

A network engineer is configuring QoS on a Cisco Catalyst 2960-X switch to support marking of traffic based on VLAN. The switch has two VLANs: VLAN 10 (voice) and VLAN 20 (data). The engineer wants to mark all traffic from VLAN 10 with CoS 5 and all traffic from VLAN 20 with CoS 0. The engineer applies a policy map that matches on VLAN using a class map. However, the marking is not being applied. What is the most likely reason?

A network engineer runs the following command on Router R1: R1# 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 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: class-default (match-any) 100 packets, 10000 bytes 5 minute offered rate 0 bps, drop rate 0 bps Match: any Queueing queue limit 64 packets (queue depth/total drops/no-buffer drops) 0/0/0 (pkts output/bytes output) 100/10000 Based on this output, what can be concluded?

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?

A network engineer runs the following command on Router R3: R3# show mls qos interface GigabitEthernet0/1 GigabitEthernet0/1 trust state: trust DSCP trust mode: trust dscp COS override: dis default COS: 0 DSCP Mutation Map: default dscp mutation map trust device: none qos mode: port-based R3# show mls qos QoS is enabled globally QoS global counters: total packets not matching QoS criteria = 0 Total packets with known CoS = 0 Total packets dropped by policing = 0 Based on this output, what can be concluded?

A network engineer runs the following command on Router R4: R4# show policy-map interface GigabitEthernet0/1 GigabitEthernet0/1 Service-policy input: SHAPE_POLICY Class-map: class-default (match-any) 1000 packets, 100000 bytes 5 minute offered rate 100000 bps, drop rate 0 bps Match: any Queueing shape (average) cir 500000, bc 5000, be 5000 target shape rate 500000 Based on this output, what can be concluded?

A network engineer runs the following command on Router R5: R5# show queueing interface GigabitEthernet0/1 Interface GigabitEthernet0/1 queueing strategy: weighted fair Queueing on output: Weighted Fair Queueing Current fair queue configuration: Number of queues: 256 Dynamic queues: 256 Reserved queues: 0 Current WFQ global configuration: Total dynamic queues: 256 Total reserved queues: 0 Class based weighted fair queueing: enabled Queueing on input: FIFO Based on this output, what can be concluded?

A network engineer runs the following command on Router R6: R6# show policy-map interface GigabitEthernet0/1 GigabitEthernet0/1 Service-policy output: QOS_POLICY Class-map: VOICE (match-any) 500 packets, 50000 bytes 5 minute offered rate 50000 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) 500/50000 police cir 1000000 bc 15625 be 15625 conformed 500 packets, 50000 bytes; actions: transmit exceeded 0 packets, 0 bytes; actions: drop violated 0 packets, 0 bytes; actions: drop Class-map: DATA (match-any) 1000 packets, 100000 bytes 5 minute offered rate 100000 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) 1000/100000 bandwidth remaining percent 50 Class-map: class-default (match-any) 2000 packets, 200000 bytes 5 minute offered rate 200000 bps, drop rate 0 bps Match: any Queueing (queue depth/total drops/no-buffer drops) 0/0/0 (pkts output/bytes output) 2000/200000 bandwidth remaining percent 50 Based on this output, what can be concluded?

A network engineer runs the following command on Router R7: R7# show mls qos interface GigabitEthernet0/1 statistics GigabitEthernet0/1 Ingress statistics: dscp: incoming no_change classified policed dropped default: 0 0 0 0 0 ef: 100 100 100 0 0 af31: 200 200 200 0 0 other: 300 300 300 0 0 Egress statistics: dscp: queued dropped default: 0 0 ef: 100 0 af31: 200 0 other: 300 0 Based on this output, what can be concluded?

A network engineer runs the following command on Router R8: R8# 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 Class-map: class-default (match-any) 0 packets, 0 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) 0/0 bandwidth remaining percent 50 Based on this output, what can be concluded?

A network engineer runs the following command on Router R9: R9# show queueing interface GigabitEthernet0/1 Interface GigabitEthernet0/1 queueing strategy: class-based weighted fair Queueing on output: Class-based Weighted Fair Queueing Queueing on input: FIFO R9# show policy-map interface GigabitEthernet0/1 GigabitEthernet0/1 Service-policy output: QOS_POLICY Class-map: VOICE (match-any) 100 packets, 10000 bytes 5 minute offered rate 10000 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) 100/10000 police cir 1000000 bc 15625 be 15625 conformed 100 packets, 10000 bytes; actions: transmit exceeded 0 packets, 0 bytes; actions: drop violated 0 packets, 0 bytes; actions: drop Class-map: DATA (match-any) 200 packets, 20000 bytes 5 minute offered rate 20000 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) 200/20000 bandwidth remaining percent 50 Class-map: class-default (match-any) 300 packets, 30000 bytes 5 minute offered rate 30000 bps, drop rate 0 bps Match: any Queueing (queue depth/total drops/no-buffer drops) 0/0/0 (pkts output/bytes output) 300/30000 bandwidth remaining percent 50 Based on this output, what can be concluded?

Examine the following configuration snippet on a Cisco IOS-XE router: interface GigabitEthernet0/1 service-policy output QOS_POLICY policy-map QOS_POLICY class VOICE priority percent 10 class VIDEO bandwidth percent 30 class class-default fair-queue What is the effect of this configuration?

Consider the following configuration on a Cisco router: class-map match-any CRITICAL_DATA match ip dscp af21 af22 af23 policy-map QOS class CRITICAL_DATA bandwidth remaining percent 50 class class-default fair-queue interface GigabitEthernet0/0 service-policy output QOS Which statement about this configuration is true?

Given the following configuration on a Cisco IOS router: policy-map SHAPE class class-default shape average 1000000 interface Serial0/0/0 service-policy output SHAPE What is the effect of this configuration?

Examine the following configuration: policy-map MARKING class VOICE set dscp ef class VIDEO set dscp af41 class class-default set dscp default interface GigabitEthernet0/0 service-policy input MARKING Which statement is true?

Consider the following configuration: class-map match-all HTTP match protocol http policy-map QOS class HTTP police 2000000 1500 3000 conform-action transmit exceed-action drop interface GigabitEthernet0/1 service-policy input QOS What is the effect of this configuration?

Examine the following configuration: policy-map QUEUE class GOLD bandwidth percent 25 queue-limit 64 packets class SILVER bandwidth percent 25 queue-limit 128 packets class class-default fair-queue interface GigabitEthernet0/2 service-policy output QUEUE Which statement about this configuration is true?

What is the default trust state of a Cisco IOS switch port when no 'mls qos trust' command is configured?

Which QoS mechanism is used to prevent head-of-line blocking by ensuring that a single queue does not consume all available buffer space?

In a Cisco QoS policy, what is the difference between 'bandwidth' and 'bandwidth remaining' commands?

Drag and drop the steps of configuring and applying a QoS policy using MQC into the correct order, from first to last.

Drag and drop the steps of implementing QoS trust boundaries on a Cisco switch into the correct order, from first to last.

Drag and drop the steps of configuring LLQ (Low Latency Queuing) on a Cisco router into the correct order, from first to last.

Drag and drop the steps of CBWFQ and LLQ queue servicing order into the correct order, from first to last.

Drag and drop the steps of QoS pre-classify for encrypted VPN traffic into the correct order, from first to last.

Drag and drop the steps of DSCP-to-CoS mapping at LAN boundary into the correct order, from first to last.

Drag and drop the steps of Hierarchical QoS (H-QoS) parent/child policy steps into the correct order, from first to last.

Drag and drop the steps of QoS policing with two-rate three-color marker (RFC 2698) into the correct order, from first to last.

Drag and drop the steps of CBWFQ and LLQ queue servicing order into the correct order, from first to last.

Drag and drop the steps of QoS pre-classify for encrypted VPN traffic into the correct order, from first to last.

Drag and drop the steps of DSCP-to-CoS mapping at LAN boundary into the correct order, from first to last.

Drag and drop the steps of Hierarchical QoS (H-QoS) parent/child policy steps into the correct order, from first to last.

Drag and drop the steps of QoS policing with two-rate three-color marker (RFC 2698) into the correct order, from first to last.

Drag and drop each queuing mechanism on the left to its matching feature on the right.

Drag and drop each congestion avoidance mechanism on the left to its matching method on the right.

Drag and drop each traffic shaping or policing characteristic on the left to its matching description on the right.

Drag and drop each DSCP PHB on the left to its matching queue treatment on the right.

Drag and drop each MQC command on the left to its matching configuration level on the right.

Drag and drop each queuing mechanism on the left to its matching feature on the right.

Drag and drop each congestion avoidance mechanism on the left to its method on the right.

Drag and drop each traffic shaping or policing characteristic on the left to its correct description on the right.

Drag and drop each DSCP PHB on the left to its matching queue treatment on the right.

Drag and drop each MQC command on the left to its configuration level on the right.

Which two statements about the MQC (Modular QoS CLI) classification process are true? (Choose two.)

Which three statements about the Differentiated Services (DiffServ) QoS model are true? (Choose three.)

Which two statements about policing and shaping are true? (Choose two.)

Which three statements about the classification and marking tools in Cisco IOS are true? (Choose three.)

Which two statements about classification and marking in QoS are true? (Choose two.)

Which three statements about policing and shaping are true? (Choose three.)

Which two statements about queuing and congestion management are true? (Choose two.)

Which three statements about QoS trust boundaries and marking are true? (Choose three.)