CCNA Discovery 3: DRSEnt Chapter 7 Exam Answers v4.0

1. Why are Network Control Protocols used in PPP?

  • to establish and terminate data links
  • to provide authentication capabilities to PPP
  • to manage network congestion and to allow quality testing of the link
  • to allow multiple Layer 3 protocols to operate over the same physical link

Explanation: PPP uses the Network Control Protocol (NCP) process to negotiate the Layer 3 protocols to operate over the link. IPCP is an example of an NCP for IP.

2. What is the data transmission rate for the DS0 standard?

  • 44 kb/s
  • 64 kb/s
  • 1.544 Mb/s
  • 44.736 Mb/s

3. In which two layers of the OSI model are key differences found between a LAN and a WAN. (Choose two.)

  • Layer 1
  • Layer 2
  • Layer 3
  • Layer 4
  • Layer 6
  • Layer 7

4. Which statement is true about the Cisco implementation of the HDLC protocol?

  • It supports authentication.
  • It has a universally compatible frame format.
  • It is the default encapsulation for serial interfaces on Cisco routers.
  • It does not support multiple protocols across a single link.

5. Refer to the exhibit. A network administrator has a connectivity problem between the serial interfaces of Merida and Vargas. What is the cause of the problem?

CCNA Discovery 3: DRSEnt Chapter 7 Exam Answers v4.0 5

  • Authentication is required on the serial link.
  • The encapsulation is misconfigured.
  • The IP addresses are on different subnets.
  • The serial interface on Vargas is shutdown.
  • The loopback interfaces on both routers are not configured.

6. Refer to the exhibit. What statement is true about the exhibited output?

CCNA Discovery 3: DRSEnt Chapter 7 Exam Answers v4.0 6

  • LCP is in the process of negotiating a link.
  • LCP and NCP are waiting for CHAP authentication to complete.
  • LCP negotiation has completed successfully, but NCP negotiation is in progress.
  • LCP and NCP negotiation is complete, and the data link service is available to carry packets.

7. Which three statements are true regarding LCP? (Choose three.)

  • It is responsible for negotiating link establishment.
  • It negotiates options for Layer 3 protocols running over PPP.
  • It uses MD5 encryption while negotiating link-establishment parameters.
  • It terminates the link upon user request or the expiration of an inactivity timer.
  • It can test the link to determine if link quality is sufficient to bring up the link.
  • It monitors the link for congestion and dynamically adjusts the acceptable window size.

8. Why are Frame Relay paths referred to as virtual?

  • Frame Relay PVCs are created and discarded on demand.
  • The connections between PVC endpoints act like dialup circuits.
  • There are no dedicated circuits to and from the Frame Relay carrier.
  • The physical circuits inside the Frame Relay cloud do not contain exclusive links for a specific Frame Relay connection.

Explanation: Unlike leased lines, there are no dedicated circuits in the carrier’s Frame Relay network for end-to-end customer connectivity. Most providers use PVCs (some use SVCs) to create and discard circuits as customers purchase them without needing to deploy additional cabling.

9. What best describes the use of a data-link connection identifier (DLCI)?

  • an address identifying a virtual circuit
  • a logical address identifying the DCE device
  • an address identifying a Layer 3 service across a Frame Relay network
  • a logical address identifying the physical interface between a router and a Frame Relay switch

10. What two services allow the router to dynamically map data link layer addresses to network layer addresses Frame Relay network? (Choose two.)

  • ARP
  • ICMP
  • Proxy ARP
  • Inverse ARP
  • LMI status messages

11. Which three statements describe functions of the Point-to-Point Protocol with regards to the OSI model?(Choose three.)

  • operates at all layers of the OSI model
  • provides a mechanism to multiplex several network layer protocols
  • can be configured on both synchronous and asynchronous serial interfaces
  • uses Layer 3 of the OSI model to establish and maintain a session between devices
  • uses the data link layer to configure such options as error detection and compression
  • uses network control protocols to test and maintain connectivity between devices

12. At what physical location does the responsibility for a WAN connection change from the user to the service provider?

  • demilitarized zone (DMZ)
  • demarcation point
  • local loop
  • cloud

13. What does a Frame Relay switch use to inform the sender that there is congestion?

  • FECN
  • BECN
  • DE
  • FCS

14. Refer to the exhibit. What statement is true about the debug output?

CCNA Discovery 3: DRSEnt Chapter 7 Exam Answers v4.0 7

  • R2 is using PAP instead of CHAP.
  • The routers have different CHAP passwords configured.
  • The administrator performed a shutdown on the R2 PPP interface during negotiation.
  • The Layer 3 protocol negotiation caused the connection failure.

15. Which two statements describe the function of time-division multiplexing? (Choose two.)

  • Multiple data streams share one common channel.
  • Conversations that require extra bandwidth receive any unused time slices.
  • Time slots are utilized on a first-come, first-served basis.
  • Time slots go unused if a sender has nothing to transmit.
  • Priority can be dedicated to one data source.

16. When customers use credit cards to make purchases at a small business, a modem is heard dialing a telephone number to transfer the transaction data to the central office. What type of WAN serial connection is in use?

  • leased line
  • point-to-point
  • circuit switched
  • packet switched

17. Which best describes data communications equipment (DCE)?

  • serves as data source and/or destination
  • responsible for negotiating windowing and acknowledgements
  • physical devices such as protocol translators and multiplexers
  • equipment that forwards data and is responsible for the clocking signal

18. Permanent virtual circuits and switched virtual circuits are both part of which option for WAN connectivity?

  • leased line
  • cell switching
  • packet switching
  • circuit switching

19. Which field of a frame uses error detection mechanisms to verify that the frame is not damaged intransit?

  • FCS
  • MTU
  • flag
  • control
  • protocol

20. What occurs in the encapsulation process as a data packet moves from a LAN across a WAN?

  • The Layer 2 encapsulation changes to a format that is appropriate for the WAN technology.
  • The Layer 3 encapsulation changes to a format that is appropriate for the WAN technology.
  • Both Layer 2 and Layer 3 encapsulation change to a technology that is appropriate for the WAN.
  • Both Layer 2 and Layer 3 encapsulation remain constant as the data packet travels throughout the network.

21. Refer to the exhibit. The network administrator is configuring R1 to connect to R2, which is a non-Cisco router. Which encapsulation method will need to be configured for communication to occur?

CCNA Discovery 3: DRSEnt Chapter 7 Exam Answers v4.0 8

  • HDLC
  • HSSI
  • ISDN
  • IPCP
  • PPP

22. A company is implementing dialup services for remote workers to connect to the local network. The company uses multiple Layer 3 protocols and requires authentication for security. Which protocol should be used for this remote access?

  • LMI
  • PPP
  • HDLC
  • Frame Relay

23. Which two options can LCP negotiate? (Choose two.)

  • compression
  • authentication
  • dynamic flow control
  • network layer address for IP
  • connection-oriented or connectionless communication methods

24. What statement best describes cell switching?

  • It uses a dedicated path between endpoints.
  • It creates a permanent physical link between two points.
  • It uses DLCIs to identify virtual circuits.
  • It creates fixed-length packets that traverse virtual circuits.
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