Miyerkules, Mayo 9, 2012

CCNA Exploration 4.0 EWAN Chapter 2

1. Which two statements are true about time-division multiplexing (TDM)? (Choose two.)
- TDM relies on Layer 3 protocols to operate.
- Multiple sources can transmit over a single channel.
- Original data streams must be reconstructed at the destination.

- TDM methods vary depending on the Layer 2 protocol that is used.
- It allows information from multiple channels to be allocated bandwidth on multiple wires.

2. What does the demarcation point represent in data communication physical circuits?
- DTE/DCE interface on the device connecting to the Internet
- location of the firewall or router
- physical point at which the public network ends and the private customer network begins- tag assigned to the physical block where a cross-connect occurs

3. 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 232 (RS-232)
- EIA/TIA 422 (RS-422)
- EIA/TIA 423 (RS-423)
- EIA/TIA-612/613 (HSSI)- ITU V.35

4. Why are serial connections preferred over parallel connections for long transmission lengths?
- Parallel connections do not support error checking.
- Parallel connections are subject to excessive attenuation.
- Parallel connections are subject to clock skew and to crosstalk between wires.
- Parallel connections transmit over only two wires and therefore transmit data more slowly.

5. Which three statements are correct about HDLC encapsulation? (Choose three.)
- HDLC does not support CDP.
- HDLC and PPP are compatible.
- HDLC supports PAP and CHAP authentication.
- 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.

6. 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.

7. Which two options can LCP negotiate? (Choose two.)
- link quality
- authentication

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

8. Which PPP configuration option can be used to establish load balancing over the interfaces of a router?
- callback
- multilink
- compression
- error detection

9. What function do Network Control Protocols provide for a PPP connection?
- to supply error detection
- 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

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

- one
- two
- three
- four

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

- Layer 2 is down.
- LCP, IPCP, and CDPCP negotiations are in progress.
- Only the link-establishment phase completed successfully.
- Both the link-establishment and network-layer phase completed successfully.

12. Which three statements correctly describe PPP authentication? (Choose three.)
- PAP sends passwords in clear text.
- PAP uses a 3-way handshake to establish a link.
- PAP provides protection from repeated trial-and-error attacks.
- CHAP uses a 2-way handshake to establish a link.
- CHAP uses a challenge/response that is based on the MD5 hash algorithm.
- CHAP uses repeated challenges for verification.

13. Which authentication protocol can be spoofed to allow playback attacks?
- MD5

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

- LCP is in the process of negotiating a link.
- LCP and NCP are waiting for CHAP authentication to complete.
- LCP negotiation has been successful, but NCP negotiation is in progress.
- Data is able to flow across this link.

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

- NCP has successfully negotiated.
- The PAP passwords did not match, so the routers are trying CHAP authentication.
- One router has suggested PAP authentication, and the other has accepted authentication but suggested CHAP authentication.
- One router can only use PAP authentication while the other router can only use CHAP, so the connection has been rejected.

16. 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.

- The router is negotiating IP compression options.
- The router is requesting an IP address from its peer.
- The router has accepted IP but not the suggested IP options.

17. What advantage does PPP have over HDLC for serial communications?
- It can communicate more efficiently with other Cisco devices
- It is less complex to configure
- It has less Layer 2 overhead
- It supports authentication

18. 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.- The router is not sensing a CD signal.
- A timing problem has occurred on the cable.
- The line is not physically connected to the CSU/DSU.
- The router configuration contains the shutdown interface configuration command.

19. 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
R3(config-if)# ppp authentication chap
- Router(config)# hostname R3
R3(config)# username R3 password Cisco
R3(config)# interface Serial 0/0/0
R3(config-if)# encapsulation ppp
R3(config-if)# ip address
R3(config-if)# ppp authentication chap
- Router (config)# username Router password Cisco
Router (config)# interface Serial 0/0/0
Router (config-if)# clockrate 64000
Router (config-if)# encapsulation ppp
Router (config-if)# ip address
Router config-if)# ppp authentication chap
- Router (config)# username R1 password Cisco
Router config)# interface Serial 0/0/0
Router (config-if)# clockrate 64000
Router config-if)# encapsulation ppp
Router (config-if)# ip address
Router (config-if)# ppp authentication chap

20. 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?

- Interface Serial0/0/0 resets very frequently.
- PPP LQM has shutdown the serial interface.
- The serial interface has no input or output queues available.
- The serial interface is not configured for a Layer 2 protocol.
- The interface has been administratively shutdown with the shutdown command.

21. 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?

- All username and password information that is sent will be encrypted.
- All authentication on the serial link will be accomplished using a three-way handshake.
- The Predictor algorithm will be used to compress all packets that are sent and received on the serial link.
- 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.

CCNA Exploration 4.0 EWAN Chapter 1

1. At which two layers of the OSI model does a WAN operate? (Choose two.)
- Physical Layer
- Data Link Layer
- Network Layer
- Transport Layer
- Presentation Layer
- Application Layer

2. Which three WAN devices can be found in the cloud? (Choose three.)
- ATM switches
- core routers
- Ethernet switches
- Frame Relay switches- repeaters

3. Which networking device is typically used to concentrate the dial-in and dial-out traffic of multiple users to and from a network?
- core router
- access server
- Frame Relay switch
- ATM switch

4. Which packet-switched WAN technology offers high-bandwidth connectivity capable of managing data, voice, and video all on the same infrastructure?
- Time Division Multiplexing (TDM)
- metro Ethernet
- Integrated Services Digital Network (ISDN)
- Public Switched Telephone Network (PSTN)

5. Which three features are identified with Frame Relay connections? (Choose three.)
- 53-byte cells

6. Which WAN technology uses a fixed payload of 48 bytes and is transported across both switched and permanent virtual circuits?
- Frame Relay
- metro Ethernet

7. What are two advantages of an analog PSTN WAN connection? (Choose two.)
- low cost
- availability
- traffic encryption
- available bandwidth
- support for voice and video

8. What three terms are associated with ISDN PRI? (Choose three.)
- circuit switching- packet switching
- data bearer channels
- switched virtual circuits
- time-division multiplexing
9. What can cause a reduction in available bandwidth on a cable broadband connection?
- smaller cells
- number of subscribers- committed information rate
- distance from the central office of the provider

10. What type of connectivity is established when VPNs are used from the remote site to the private network?
- PVCs
- tunnels
- virtual circuits
- dedicated Layer 2 links

11. A U.S. company requires a WAN connection used only to transfer sales data from individual stores to the home office. All transfers will occur after business hours. The required bandwidth for this connection is estimated to be less than 38 kbps. Which type of connection requires the least investment for this company?
- analog dialup- T1 Leased Line

12. For digital lines, which device is used to establish the communications link between the customer equipment and the local loop?
- Frame Relay switch
- ISDN switch
- modem
- PBX switch

13. Which term describes a device that will put data on the local loop?

14. Which switching type will allow the communication devices in the provider network to be shared and only allocated to an individual subscriber during data transfer?
- circuit-switched
- dedicated switched lines
- frame-switched
- packet-switched

15. A company needs a WAN connection that is capable of transferring voice, video, and data at a minimum data rate of 155 Mbps. Which WAN connection is the best choice?
- X.25

16. Which two devices are commonly used as data communications equipment? (Choose two.)
- modem
- router
- ISDN switch
- Ethernet switch

17. Which statement is true of the functionality of the layers in the hierarchical network model?
- The purpose of the access layer is to provide very high bandwidth communications between network devices.
- Most security screening to prevent unauthorized entry to the network happens at the core layer.
- Untrusted external connections are segmented from the rest of the network at all three levels.
- The core layer uses high speed equipment to provide policy-based connectivity.
- The distribution layer aggregates WAN connections at the edge of the campus.
18. Which statement is true about data connectivity between a customer and a service provider?
- Normally the CSU/DSU is the designated demarcation point for the service provider but not the customer.
- The segment between the demarcation point and the central office is known as the "last mile."- The local loop is the segment between the CSU/DSU and the serial port on a router.
- Putting data on the local loop is the responsibility of the DTE.

19. Which statement is true about the differences between a WAN and a LAN?
- WANs generally support higher bandwidth than LANs support.
- A WAN link typically traverses shorter geographic distances than a LAN link traverses.
- A WAN often relies on the services of carriers, such as telephone or cable companies, but a LAN does not.- All WAN implementations generally use the same Layer 2 protocol but there are many accepted LAN Layer 2 protocols in use.

20. Why is the call setup time of a circuit-switched WAN implementation considered a drawback?
- Routing protocols are incompatible with this function.
- It restricts the communication sent to voice traffic only.
- A telephone must be used to initially start transferring data.
- Data cannot be transferred until a circuit has been established.

21. Which statement about WAN protocols is correct?
- ATM differs from other WAN protocols in that it uses variably sized packets.
- Most WAN protocols use HDLC or a variant of HDLC as a framing mechanism.- The frame header consists of the frame check sequence and cyclic redundancy check.
- ISDN differs from Frame Relay, HDLC, and ATM in that it is packet-switched rather than circuit-switched technology.

22. What is an advantage of packet-switched technology over circuit-switched technology?
- Packet-switched networks are less susceptible to jitter than circuit-switched networks are.
- Packet-switched networks can efficiently use multiple routes inside a service provider network.- Packet-switched networks do not require an expensive permanent connection to each endpoint.
- Packet-switched networks usually experience lower latency than circuit-switched networks experience.