Minggu, 28 Maret 2010

CCNA 4 Chapter 2

1. Refer to the exhibit. What can be concluded about the function of the Serial 0/0/0 interface on the router after the commands are entered?

The serial link will be closed if the number of received packets at the destination node falls below 90 percent of the packets that are sent.

2. Refer to the exhibit. While troubleshooting a serial interface, a technician enters the command show interface serial 0/0/0 . If the interface is in DCE mode, what two problems are likely to cause the indicated problem? (Choose two.)

The remote CSU or DSU has failed.
A timing problem has occurred on the cable.

3. Refer to the exhibit. What statement is true regarding the output shown?

The PAP passwords did not match, so the routers are trying CHAP authentication.

4. Why are serial connections preferred over parallel connections for long transmission lengths?

Parallel connections are subject to clock skew and to crosstalk between wires.

5. Which two statements are true about time-division multiplexing (TDM)? (Choose two.)

Multiple sources can transmit over a single channel.
Original data streams must be reconstructed at the destination.

6. Which authentication protocol can be spoofed to allow playback attacks?

PAP

7. What function do Network Control Protocols provide for a PPP connection?

to allow multiple Layer 3 protocols to operate over the same physical link

8. Refer to the exhibit. Router R1, the DCE device, has just been configured for PPP encapsulation with authentication. What series of commands will allow another router, the DTE device, to communicate over its serial 0/0/0 interface to router R1?

Router(config)# hostname R3
R3(config)# username R1 password Cisco
R3(config)# interface Serial 0/0/0
R3(config-if)# encapsulation ppp
R3(config-if)# ip address 172.16.3.3 255.255.255.0
R3(config-if)# ppp authentication chap

9. What advantage does PPP have over HDLC for serial communications?

It supports authentication

10. Which PPP configuration option can be used to establish load balancing over the interfaces of a router?

multilink

11. Which three statements are correct about HDLC encapsulation? (Choose three.)

HDLC implementation in Cisco routers is proprietary.
HDLC is the default serial interface encapsulation on Cisco routers.
HDLC uses frame delimiters to mark the beginnings and ends of frames.

12. Refer to the exhibit. Router R1 is not able to communicate with a neighbor router that is directly connected to serial 0/0/0. What is the reason for this?

The interface has been administratively shutdown with the shutdown command.

13. Refer to the exhibit. What statement is true regarding the output shown?

Data is able to flow across this link.

14.
Which serial communications DTE/DCE interface standard is used to provide high-speed connectivity of up to 52 Mbps between LANs and is found on many high-end Cisco routers?

EIA/TIA-612/613 (HSSI)

15. What does the demarcation point represent in data communication physical circuits?

physical point at which the public network ends and the private customer network begins

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

It is responsible for negotiating link establishment.
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.

17. Refer to the exhibit. Which two statements are true regarding the output shown? (Choose two.)

The router has agreed on IP parameters.
The router has negotiated LCP successfully.

18. Refer to the exhibit. Which statement is true about PPP operation?

Both the link-establishment and network-layer phase completed successfully.

19. Which three statements correctly describe PPP authentication? (Choose three.)

PAP sends passwords in clear text.
CHAP uses a challenge/response that is based on the MD5 hash algorithm.
CHAP uses repeated challenges for verification.

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

link quality
authentication

21. Refer to the exhibit. On the basis of the show interface Serial0/0 output, how many NCP sessions have been established?

two

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