Accessing the WAN - Chapter 2

8/8/2019 Accessing the WAN - Chapter 2

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Accessing the WAN - Chapter 2

1

Whichtwostatements are true about time-division multiplexing (TDM)? (Choosetwo.)

TDM relies on Layer 3 protocols to operate.

Multiple channelscan transmit over a single link.

Original data streams must bereconstructedat the destination.

TDM methodsvarydepending on the Layer 2 protocolthatisused.

It allows information from multiple channels to beallocatedbandwidth on multiple

wires.

Observable Description Max Value

1 correctness of response Option 2 and Option 3 are correct.

1 point for each correct option.0 points if more options are selectedthanrequired. 2

This item references content from the following areas:

CCNA Exploration: Accessing the WAN

* 2.1.2 TDM

2

Whatdoes the demarcation point represent in data communication physical circuits?

DTE/DCE interface on the deviceconnecting to the Internet

location of the firewall or router

physical point atwhich the public network ends and the privatecustomer network

begins

tag assigned to the physical block where a cross-connectoccurs


1 correctness of response 2 points for Option 3

0 points for anyother option 2



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* 2.1.3 Demarcation Point

3Which serial communications DTE/DCE interface standard isused to providehigh-

speed connectivity of up to 52 Mbps betweenLANs and isfound on manyhigh-end

Cisco routers?

EIA/TIA 232 (RS-232)



EIA/TIA-612/613 (HSSI)

ITU V.35






* 2.1.1 Introducing Serial Communications

4

Why are serial connections preferred over parallel connections for long transmission

lengths?

Parallel connections do not support errorchecking.

Parallel connections are subject to excessive attenuation.

Parallel connections are subject to clockskew and to crosstalkbetweenwires.

Parallel connections transmit over onlytwowires and therefore transmit data more

slowly.





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* 2.1.1 Introducing Serial Communications

5

Whichthreestatements are correct about HDLC encapsulation? (Choosethree.)

HDLC does not support CDP.

HDLC and PPP are compatible.

HDLC supports PAP and CHAP authentication.

HDLC implementation in Cisco routersisproprietary.

HDLC is the default serial interface encapsulation on Cisco routers.

HDLC uses frame delimiters to mark the beginnings and ends of frames.


1 correctness of response Option 4, Option 5, and Option 6 are correct.

1 point for each correct option.

0 points if more options are selectedthanrequired. 3



* 2.1.5 HDLC Encapsulation

6

Whichthreestatements are trueregarding LCP? (Choosethree.)

It isresponsible for negotiatinglink establishment.

It negotiates options for Layer 3 protocols running over PPP.

It uses MD5 encryptionwhilenegotiatinglink establishment parameters.

It terminates the linkuponuserrequest or the expiration of an inactivitytimer.

It can test the link to determine if linkqualityissufficient to bring up the link.

It monitors the link for congestion and dynamicallyadjusts the acceptable

windowsize.


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* 2.2.5 Establishing a Link with LCP

7

Whichtwo options can LCP negotiate? (Choosetwo.)

linkquality

authentication

dynamic flow control

compression and network layer address for IP

connection-oriented or connectionless communication methods


1 correctness of response Option 1 and Option 2 are correct.1 point for each correct option.




* 2.2.5 Establishing a Link with LCP

8

Which PPP configuration option canbeused to establishloadbalancing over the

interfaces of a router?

callback

multilink


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compression

errordetection


1 correctness of response 2 points for Option 20 points for anyother option 2



* 2.3.1 PPP Configuration Options

9

Whatfunction do Network Control Protocolsprovide for a PPP connection?

to supplyerrordetection

to establish and terminate data links

to provideauthenticationcapabilities to PPP

to manage network congestion and to allowqualitytesting of the link

to allow multiple Layer 3 protocols to operate over the samephysicallink

Observable Description Max Value1 correctness of response 2 points for Option 5




* 2.2.2 PPP Layered Architecture

10


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Refer to the exhibit. On the basis of the show interface Serial0/0 output, how

manyNCP sessions have been established?

one

two

three

four






* 2.3.3 Verifying a Serial PPP Encapsulation Configuration

11


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Refer to the exhibit. Whichstatementistrue about PPP operation?

Layer 2 is down.

LCP, IPCP, and CDPCP negotiations are in progress.

Only the link-establishment phase completedsuccessfully.

Both the link-establishment and network-layer phase completedsuccessfully.







12Whichthreestatementscorrectlydescribe PPP authentication? (Choosethree.)

PAP sendspasswords in cleartext.

PAP uses a 3-way handshake to establish a link.

PAP provides protection fromrepeated trial-and-errorattacks.

CHAP uses a 2-way handshake to establish a link.

CHAP uses a challenge/responsethatisbased on the MD5 hash algorithm.


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CHAP uses repeated challenges for verification.



1 point for each correct option.0 points if more options are selectedthanrequired. 3



* 2.4.3 Challenge HandshakeAuthentication Protocol (CHAP)

13

Whichauthenticationprotocolcanbespoofed to allow playback attacks?

MD5

CHAP

PAP

NCP


1 correctness of response 2 points for Option 30 points for anyother option 2



* 2.4.2 PasswordAuthentication Protocol (PAP)

14

Refer to the exhibit. Whatstatementistrueregarding the output shown?


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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 negotiationis in progress.

Data is able to flow acrossthislink.






* 2.3.4 Troubleshooting PPP Encapsulation

15

Refer to the exhibit. Whatstatementistrueregarding the output shown?

NCP has successfullynegotiated.

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

One router has suggested PAP authentication, and the other has

acceptedauthentication but suggested CHAP authentication.

One router canonly use PAP authenticationwhile the other router canonly use CHAP,

so the connection has been rejected.






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16

Refer to the exhibit. Whichtwostatements are trueregarding the output shown?

(Choosetwo.)

The router has agreed on IP parameters.

The router has negotiated LCP successfully.

The router isnegotiating IP compression options.

The router isrequesting an IP addressfromitspeer.

The router has accepted IP but not the suggested IP options.








17

Whatadvantagedoes PPP have over HDLC for serial communications?

It cancommunicate more efficientlywithother Cisco devices

It islesscomplex to configure

It has less Layer 2 overhead

It supports authentication



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* 2.2.1 Introducing PPP

18

Refer to the exhibit. Whiletroubleshooting a serial interface, a technicianenters the

command show interface serial 0/0/0 . If the interface is in DCE mode,

whattwoproblems are likely to cause the indicatedproblem? (Choosetwo.)

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 physicallyconnected to the CSU/DSU.

The router configuration contains the shutdown interface configuration command.







* 2.1.7 Troubleshooting a Serial Interface

19


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Refer to the exhibit. Router R1, the DCE device, has just been configured for PPP

encapsulation withauthentication. Whatseries of commandswillallowanother 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)# ipaddress 172.16.3.3 255.255.255.0

R3(config-if)# ppp authenticationchap

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)# ipaddress 172.16.3.3 255.255.255.0

R3(config-if)# ppp authenticationchap

Router (config)# username Router password CiscoRouter (config)# interface Serial 0/0/0

Router (config-if)# clockrate 64000

Router (config-if)# encapsulation ppp

Router (config-if)# ipaddress 172.16.3.1 255.255.255.0

Router config-if)# ppp authenticationchap

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)# ipaddress 172.16.3.1 255.255.255.0

Router (config-if)# ppp authenticationchap




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* 2.4.5 Configuring PPP withAuthentication

20

Refer to the exhibit. Router R1 is not able to communicatewith a

neighborrouterthatisdirectlyconnected to serial 0/0/0. Whatis the reason for this?

Interface Serial0/0/0 resetsveryfrequently.

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 administrativelyshutdownwith the shutdown command.






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21

Refer to the exhibit. Whatcanbeconcluded about the function of the Serial 0/0/0

interface on the router after the commands are entered?All username and password information thatis sent willbeencrypted.

All authentication on the serial linkwillbeaccomplishedusing a two -wayhandshake.

The Predictoralgorithmwillbeused to compress all packetsthat are sent and received

on the serial link.

The serial linkwillbeclosed if the number of receivedpacketsat the destination

nodefallsbelow 90 percent of the packetsthat are sent.






* 2.3.2 PPP Configuration Commands

Accessing the WAN - Chapter 2

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