CCNA 4, Chapter 6 Exam

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CCNA Quizzes & Trivia

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Questions and Answers
  • 1. 

    A network engineer performs a ping test and receives a value that shows the time it takes for a packet to travel from a source to a destination device and return. Which term describes the value?

    • A.

      Latency

    • B.

      Jitter

    • C.

      Priority

    • D.

      Bandwidth

    Correct Answer
    A. Latency
    Explanation
    Latency refers to the time it takes for a packet to travel from a source to a destination device and return. It is a measure of the delay or lag in the network.

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  • 2. 

    When QoS is implemented in a converged network, which two factors can be controlled to improve network performance for real-time traffic? (Choose two.)

    • A.

      Delay

    • B.

      Jitter

    • C.

      Link speed

    • D.

      Packet routing

    • E.

      Packet addressing

    Correct Answer(s)
    A. Delay
    B. Jitter
    Explanation
    By controlling delay and jitter, network performance for real-time traffic can be improved in a converged network. Delay refers to the time it takes for a packet to travel from the source to the destination, and by reducing delay, real-time traffic can be delivered more quickly, resulting in better performance. Jitter refers to the variation in delay, and by minimizing jitter, the network can provide a more consistent and predictable delivery of real-time traffic, further enhancing performance.

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  • 3. 

    How does a Cisco router using tail drop handle congestion when a traffic queue becomes full?

    • A.

      The router will only drop non delay-sensitive data that is close to the end of the queue

    • B.

      The router will drop any packet that arrives at the end of the queue.

    • C.

      The router will remove the most recent data placed in the queue to make space for an arriving packet.

    • D.

      The router will remove the packet in the front of the queue, move all other packets forward, and insert the just arrived packet at the end.

    Correct Answer
    B. The router will drop any packet that arrives at the end of the queue.
    Explanation
    When a traffic queue becomes full, a Cisco router using tail drop handles congestion by dropping any packet that arrives at the end of the queue. This means that the router prioritizes dropping the most recent packets that arrive, regardless of their content or sensitivity to delay. By doing so, the router ensures that the queue does not exceed its capacity and helps manage congestion in the network.

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  • 4. 

    What are two characteristics of voice traffic? (Choose two.)

    • A.

      Dropped voice packets are not retransmitted.

    • B.

      Voice traffic requires at least 384 kbs of bandwidth.

    • C.

      Voice traffic consumes lots of network resources.

    • D.

      Voice traffic is unpredictable and inconsistent.

    • E.

      Voice traffic latency should not exceed 150 ms.

    Correct Answer(s)
    A. Dropped voice packets are not retransmitted.
    E. Voice traffic latency should not exceed 150 ms.
    Explanation
    Voice traffic is characterized by the fact that dropped voice packets are not retransmitted. This means that if a packet is lost during transmission, it will not be requested again. Additionally, voice traffic has the characteristic that its latency should not exceed 150 ms. This means that there should be minimal delay in the transmission of voice packets to ensure smooth and real-time communication.

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  • 5. 

    For classifying packets into classes with CBWFQ, what is the purpose of configuring a maximum packet limit for a class?

    • A.

      To control the maximum number of packets allowed in a single queue

    • B.

      To control the maximum number of packets allowed to be discarded

    • C.

      To control the maximum number of packets that can be forwarded each second on an egress interface

    • D.

      to control the maximum number of packets that can be received each second on an ingress interface

    Correct Answer
    A. To control the maximum number of packets allowed in a single queue
    Explanation
    Configuring a maximum packet limit for a class in CBWFQ allows for the control of the maximum number of packets allowed in a single queue. This helps in managing the congestion within the network by preventing the queue from becoming overloaded with packets. By setting a limit, it ensures that the queue does not exceed its capacity, allowing for better control and prioritization of traffic.

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  • 6. 

    A network engineer is selecting a QoS method to control congestion on a VPN tunnel link between the headquarters site and a branch office. Which queuing method cannot be used to classify and control VPN traffic?

    • A.

      FIFO

    • B.

      WFQ

    • C.

      CBWFQ

    • D.

      LLQ

    Correct Answer
    B. WFQ
    Explanation
    WFQ (Weighted Fair Queuing) is a queuing method that can be used to classify and control VPN traffic. WFQ assigns weights to different traffic flows and shares the bandwidth fairly among them. It ensures that each flow gets its fair share of the available bandwidth based on its weight. Therefore, WFQ can be used to control congestion on a VPN tunnel link between the headquarters site and a branch office.

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  • 7. 

    An administrator has mastered the use of access control lists (ACLs) and wants to deploy QoS by defining different traffic classes through the use of ACLs. Which queuing method provides this functionality?

    • A.

      FIFO

    • B.

      WFQ

    • C.

      FCFS

    • D.

      CBWFQ

    Correct Answer
    D. CBWFQ
    Explanation
    CBWFQ (Class-Based Weighted Fair Queuing) is the queuing method that provides the functionality of defining different traffic classes through the use of ACLs. CBWFQ allows the administrator to classify traffic based on ACLs and assign different bandwidth allocations to each class. This ensures that different types of traffic receive the appropriate level of service and prioritization, based on their defined class.

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  • 8. 

    Which queuing algorithm has only a single queue and treats all packets equally?

    • A.

      FIFO

    • B.

      CBWFQ

    • C.

      WFQ

    • D.

      LLQ

    Correct Answer
    A. FIFO
    Explanation
    FIFO stands for First-In-First-Out, which means that the first packet that enters the queue is the first one to be transmitted. It treats all packets equally, regardless of their priority or type. This queuing algorithm does not prioritize any specific packets and ensures that packets are transmitted in the order they were received.

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  • 9. 

    A network administrator is deploying QoS with the ability to provide a special queue for voice traffic so that voice traffic is forwarded before network traffic in other queues. Which queuing method would be the best choice?

    • A.

      FIFO

    • B.

      WFQ

    • C.

      CBWFQ

    • D.

      LLQ

    Correct Answer
    D. LLQ
    Explanation
    The best choice for providing a special queue for voice traffic would be LLQ (Low Latency Queueing). LLQ allows voice traffic to be prioritized and forwarded before other network traffic in different queues. This ensures that voice traffic receives the necessary quality of service and low latency, which is crucial for real-time communication.

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  • 10. 

    What are two characteristics of DiffServ QoS model? (Choose two.)

    • A.

      the easiest QoS model to deploy

    • B.

      groups all TCP flows into a single class

    • C.

      Delivers end to end QoS

    • D.

      uses the Resource Reservation Protocol (RSVP) to signal QoS requirements

    • E.

      can divide network traffic into classes based on business requirements

    Correct Answer(s)
    B. groups all TCP flows into a single class
    E. can divide network traffic into classes based on business requirements
    Explanation
    The DiffServ QoS model has two characteristics. Firstly, it groups all TCP flows into a single class, which helps in managing and prioritizing traffic. Secondly, it can divide network traffic into classes based on business requirements, allowing for differentiated treatment of different types of traffic.

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  • 11. 

    What are two characteristics of the best-effort QoS model? (Choose two.)

    • A.

      It does not provide a delivery guarantee for packets.

    • B.

      It uses a connection-oriented approach with QoS.

    • C.

      It treats all network packets in the same way.

    • D.

      It allows end hosts to signal their QoS needs to the network.

    • E.

      It provides preferential treatment for voice packets.

    Correct Answer(s)
    A. It does not provide a delivery guarantee for packets.
    C. It treats all network packets in the same way.
    Explanation
    The best-effort QoS model does not provide a delivery guarantee for packets, meaning that there is no assurance that packets will be delivered successfully or in a timely manner. Additionally, this model treats all network packets in the same way, without prioritizing any specific type of traffic. This lack of differentiation means that all packets are treated equally, regardless of their content or importance.

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  • 12. 

    What role do network devices play in the IntServ QoS model?

    • A.

      Network devices ensure that resources are available before traffic is allowed to be sent by a host through the network.

    • B.

      Network devices provide a best-effort approach to forwarding traffic.

    • C.

      Network devices are configured to service multiple classes of traffic and handle traffic as it may arrive.

    • D.

      Network devices use QoS on a hop-by-hop basis to provide excellent scalability.

    Correct Answer
    A. Network devices ensure that resources are available before traffic is allowed to be sent by a host through the network.
    Explanation
    Network devices play a crucial role in the IntServ QoS model by ensuring that resources are available before allowing traffic to be sent by a host through the network. This means that network devices prioritize and manage traffic based on the quality of service requirements set by the applications or users. By doing so, network devices can guarantee that the necessary bandwidth, latency, and other QoS parameters are met, ensuring a reliable and consistent network performance for different types of traffic.

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  • 13. 

    Which QoS model is very resource intensive and provides the highest guarantee of QoS?

    • A.

      DiffServ

    • B.

      best-effort

    • C.

      IntServ

    • D.

      soft QoS

    Correct Answer
    C. IntServ
    Explanation
    IntServ (Integrated Services) is a QoS model that is very resource intensive and provides the highest guarantee of QoS. It achieves this by reserving specific resources for each flow and ensuring that the network can handle the required bandwidth and latency. This model is suitable for applications that require strict QoS guarantees, such as real-time video and voice communication. DiffServ, on the other hand, is a more scalable and flexible QoS model that classifies and prioritizes traffic based on different service levels. Best-effort and soft QoS do not provide the same level of guarantee as IntServ.

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  • 14. 

    In QoS models, which type of traffic is commonly provided the most preferential treatment over all other application traffic?

    • A.

      Voice traffic

    • B.

      email

    • C.

      web traffic

    • D.

      file transfers

    Correct Answer
    A. Voice traffic
    Explanation
    Voice traffic is commonly provided the most preferential treatment over all other application traffic in QoS models because it requires low latency and minimal packet loss to maintain clear and uninterrupted communication. QoS prioritizes voice traffic to ensure high-quality voice calls and prevent any disruptions or delays in voice transmission. This is especially crucial for real-time communication applications such as VoIP (Voice over Internet Protocol) or video conferencing, where any delay or loss of packets can significantly impact the user experience.

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  • 15. 

    What are two approaches to prevent packet loss due to congestion on an interface? (Choose two.)

    • A.

      Prevent bursts of traffic.

    • B.

      Drop lower-priority packets.

    • C.

      Decrease buffer space.

    • D.

      Disable queuing mechanisms.

    • E.

      Increase link capacity.

    Correct Answer(s)
    B. Drop lower-priority packets.
    E. Increase link capacity.
    Explanation
    To prevent packet loss due to congestion on an interface, two approaches can be taken. Firstly, dropping lower-priority packets can be done to ensure that higher-priority packets are transmitted without loss. This helps in maintaining the quality of service for important data. Secondly, increasing the link capacity can be effective as it allows more data to be transmitted simultaneously, reducing the chances of congestion and packet loss. By expanding the bandwidth, the interface can handle more traffic, thereby minimizing congestion-related issues.

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  • 16. 

    What two fields are available in IPv4 and IPv6 headers to mark packets for QoS? (Choose two.)

    • A.

      Class of Service

    • B.

      Traffic Class

    • C.

      Type of Service

    • D.

      Priority

    • E.

      VLAN ID

    Correct Answer(s)
    B. Traffic Class
    C. Type of Service
    Explanation
    The two fields available in both IPv4 and IPv6 headers to mark packets for Quality of Service (QoS) are Traffic Class and Type of Service. These fields allow for the prioritization and classification of network traffic based on its specific requirements and characteristics. By assigning appropriate values to these fields, network administrators can ensure that certain packets receive preferential treatment, such as higher priority or guaranteed bandwidth, to meet the desired QoS objectives.

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  • 17. 

    What is the benefit of deploying Layer 3 QoS marking across an enterprise network?

    • A.

      Layer 3 marking can carry QoS information on switches that are not IP aware.

    • B.

      Layer 3 marking can be used to carry non-IP traffic.

    • C.

      Layer 3 marking can carry the QoS information end-to-end.

    • D.

      Layer 3 marking can be carried in the 802.1Q fields.

    Correct Answer
    C. Layer 3 marking can carry the QoS information end-to-end.
    Explanation
    Layer 3 marking can carry the QoS information end-to-end. This means that the QoS information can be maintained and applied consistently throughout the entire network, from the source to the destination. This ensures that the desired QoS levels are maintained for the traffic, regardless of the switches or routers it passes through. This end-to-end consistency is important for maintaining the quality and prioritization of different types of traffic, such as voice or video, across the network.

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  • 18. 

    Which QoS technology provides congestion avoidance by allowing TCP traffic to be throttled before buffers become full and tail drops occur?

    • A.

      traffic policing

    • B.

      weighted random early detection

    • C.

      best-effort

    • D.

      first-in, first-out

    Correct Answer
    B. weighted random early detection
    Explanation
    Weighted Random Early Detection (WRED) is a QoS technology that provides congestion avoidance by allowing TCP traffic to be throttled before buffers become full and tail drops occur. WRED randomly drops packets based on their IP precedence or DiffServ code point values, giving higher priority to more important traffic. This helps to prevent congestion by slowing down the transmission rate of TCP traffic and signaling to the sender to reduce its rate, thereby avoiding buffer overflow and packet loss.

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  • 19. 

    Refer to the exhibit. As traffic is forwarded out an egress interface with QoS treatment, which congestion avoidance technique is used?

    • A.

      traffic policing

    • B.

      classification and marking

    • C.

      weighted random early detection

    • D.

      traffic shaping

    Correct Answer
    A. traffic policing
    Explanation
    The correct answer is traffic policing. Traffic policing is a congestion avoidance technique used to control and limit the rate of traffic being forwarded out of an egress interface. It enforces a specified rate limit on the traffic, dropping or remarking packets that exceed the limit. This helps prevent congestion and ensures that the network resources are used efficiently.

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  • 20. 

    Which QoS model uses the DSCP bits to mark packets and provides 64 possible classes of service?

    • A.

      IntServ

    • B.

      best-effort

    • C.

      DiffServ

    • D.

      FIFO

    Correct Answer
    C. DiffServ
    Explanation
    DiffServ (Differentiated Services) is the QoS model that uses the DSCP (Differentiated Services Code Point) bits to mark packets and provides 64 possible classes of service. DiffServ is a scalable and flexible QoS model that allows network administrators to prioritize different types of traffic based on their importance or requirements. By using the DSCP bits, DiffServ enables routers and switches to easily identify and treat packets differently, ensuring that high-priority traffic receives better service and network resources are efficiently utilized.

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  • 21. 

    Which QoS technique retains excess packets in a separate queue for later transmission?

    • A.

      Classifying

    • B.

      Marking

    • C.

      Queuing

    • D.

      Shaping

    Correct Answer
    D. Shaping
    Explanation
    Shaping is a QoS technique that retains excess packets in a separate queue for later transmission. It controls the rate of outgoing traffic by delaying packets that exceed a certain rate limit. This helps to smooth out the traffic flow and prevent congestion in the network. By storing excess packets in a separate queue, shaping ensures that they are not discarded immediately, but rather transmitted at a later time when the network is less congested. This technique is useful in situations where the network capacity is limited and needs to be managed efficiently.

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