CCNP QoS Practice Test 2 — 15 Questions

Question 1

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?

Accepted Answer

All packets are being queued without drops at egress.. The ingress statistics show that packets with DSCP EF, AF31, and other values are being classified and no policing drops occur. The egress statistics show that all packets are queued without drops. This indicates that the QoS policy is not dropping any traffic, and the interface is likely not congested.

Answer

Packets with DSCP EF are being dropped at ingress.

Answer

Policing is dropping packets with DSCP AF31.

Answer

The interface is not using any QoS policy.

Question 2

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?

Accepted Answer

The interface is not passing any traffic.. All classes show zero packets, zero bytes, and zero rates. This indicates that no traffic has been processed through this interface. The policy-map is applied but no packets have been seen.

Answer

Voice traffic is being prioritized but not policed.

Answer

Data traffic is being dropped due to policing.

Answer

The policy-map is applied to input traffic.

Question 3

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?

Accepted Answer

Data traffic is guaranteed 50% of the remaining bandwidth after priority queuing.. The output queueing strategy is CBWFQ. The VOICE class uses strict priority and is policed at 1 Mbps. All voice packets conform (100 packets). DATA and class-default share remaining bandwidth equally. The total offered rate is 60 kbps, well below any congestion, so no drops occur.

Answer

The interface uses WFQ for output queuing.

Answer

Voice traffic is being dropped because it exceeds the police rate.

Answer

The policy-map is applied to input traffic.

Question 4

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?

Accepted Answer

VOICE traffic is guaranteed 10% of the interface bandwidth with strict priority queuing, VIDEO traffic is guaranteed 30%, and all other traffic shares the remaining bandwidth using fair-queuing.. The policy-map applies a priority queue for VOICE traffic, guarantees bandwidth for VIDEO, and uses fair-queue for all other traffic on the output interface.

Answer

VOICE traffic is limited to 10% of bandwidth, VIDEO to 30%, and all other traffic is dropped if the interface is congested.

Answer

VOICE traffic is given priority over VIDEO, but VIDEO can use up to 30% of bandwidth only if VOICE is not using its allocation.

Answer

The policy-map is invalid because 'priority' and 'bandwidth' cannot be used together in the same policy-map.

Question 5

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?

Accepted Answer

Traffic matching DSCP AF21, AF22, or AF23 is guaranteed 50% of the interface bandwidth, and all other traffic is subject to fair-queuing.. The class-map matches DSCP values AF21, AF22, and AF23 (which are Assured Forwarding classes). The policy-map allocates 50% of remaining bandwidth to this class after any priority queues, and uses fair-queue for the default class.

Answer

Only traffic with DSCP AF21 is matched; AF22 and AF23 are ignored because 'match-any' requires all conditions to be true.

Answer

The configuration is invalid because 'bandwidth remaining percent' cannot be used with 'fair-queue' in the same policy-map.

Answer

The policy-map will only be applied to incoming traffic on GigabitEthernet0/0.

Question 6

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?

Accepted Answer

The router will limit the transmit rate on Serial0/0/0 to an average of 1 Mbps by queuing excess packets.. The 'shape average' command limits the output rate on the interface to an average of 1 Mbps (1000000 bps) by buffering excess traffic.

Answer

The router will drop any traffic exceeding 1 Mbps on Serial0/0/0.

Answer

The router will mark all traffic with a rate limit of 1 Mbps but not enforce it.

Answer

The configuration is invalid because 'shape average' requires a class-map with a match statement.

Question 7

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?

Accepted Answer

Incoming packets matching the VOICE class will have their DSCP set to EF (46), VIDEO to AF41 (34), and all others to default (0).. This policy-map sets DSCP values for incoming traffic based on the class. VOICE traffic is marked as EF (46), VIDEO as AF41 (34), and all other traffic as default (0).

Answer

The policy-map will only mark packets if the interface is congested.

Answer

The configuration is invalid because 'set dscp' cannot be used in a 'service-policy input' direction.

Answer

The policy-map will remark the DSCP of outgoing packets on GigabitEthernet0/0.

Question 8

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?

Accepted Answer

HTTP traffic is policed to an average rate of 2 Mbps; packets that exceed the rate are dropped, while conforming packets are transmitted.. The police command limits HTTP traffic to an average rate of 2 Mbps with a normal burst of 1500 bytes and an excess burst of 3000 bytes. Traffic within the rate is transmitted; traffic exceeding the rate is dropped.

Answer

HTTP traffic is shaped to an average rate of 2 Mbps; excess packets are buffered.

Answer

The police command will mark HTTP packets with a DSCP value of 0 if they exceed the rate.

Answer

The configuration is invalid because 'police' cannot be used in a 'service-policy input' direction.

Question 9

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?

Accepted Answer

The GOLD class has a smaller queue limit than SILVER, which may cause more packet drops for GOLD traffic under congestion.. The policy-map allocates 25% of bandwidth to both GOLD and SILVER classes, with queue limits of 64 and 128 packets respectively. The default class uses fair-queue. This configuration is valid and provides differentiated queuing.

Answer

The SILVER class will always receive more bandwidth than GOLD because of its larger queue limit.

Answer

The configuration is invalid because 'queue-limit' cannot be used with 'bandwidth percent' in the same class.

Answer

The 'fair-queue' command in class-default will override the bandwidth allocation for GOLD and SILVER.

Question 10

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

Accepted Answer

The port is untrusted and marks all incoming packets with CoS 0.. By default, Cisco switches do not trust any QoS markings on incoming packets; they are set to the default CoS/DSCP value of 0 unless a trust policy is applied.

Answer

The port trusts the CoS value of incoming packets.

Answer

The port trusts the DSCP value of incoming packets.

Answer

The port trusts both CoS and DSCP values.

Question 11

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

Accepted Answer

Weighted Random Early Detection (WRED). Congestion avoidance mechanisms like Weighted Random Early Detection (WRED) proactively drop packets before queues become full, preventing tail drops and head-of-line blocking.

Answer

Policing

Answer

Shaping

Answer

Priority Queuing

Question 12

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

Accepted Answer

'bandwidth' allocates from the total bandwidth, while 'bandwidth remaining' allocates from the bandwidth left after priority queues.. The 'bandwidth' command allocates a percentage of the total interface bandwidth, while 'bandwidth remaining' allocates a percentage of the bandwidth left after priority queues and other guaranteed allocations have been served.

Answer

There is no difference; both commands allocate bandwidth based on the total interface bandwidth.

Answer

'bandwidth' is used for output policies, while 'bandwidth remaining' is used for input policies.

Answer

'bandwidth' guarantees a minimum rate, while 'bandwidth remaining' sets a maximum rate.

Question 13

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

Accepted Answer

Create class-map to match traffic. The MQC process first defines traffic classes with class maps, then associates actions with policy maps, and finally applies the policy to an interface with a service-policy statement. Verification ensures correct operation.

Question 14

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

Accepted Answer

Identify the trust boundary location. First, identify the trust boundary (e.g., access port). Then configure the trusted interface to trust CoS or DSCP. Next, set the default CoS for untrusted frames. Finally, verify the configuration and adjust as needed.

Question 15

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

Accepted Answer

Create class-map for real-time traffic. LLQ requires first classifying traffic, then assigning it to a priority queue in a policy map, applying bandwidth/queue-limit, attaching the policy to an interface, and finally verifying queue statistics.