Wide Area Networks Questions and Answers

Q: In which of the following technologies is the term HFC used?

Correct answer: CableHFC stands for hybrid fibre-coaxial, the plant a cable operator uses: fibre from the head end to a neighbourhood node, then coaxial cable to the individual premises. It is specific to cable broadband. DSL runs over the existing telephone pair, and Frame Relay and a dedicated T1 are carrier services with no such plant of their own.

Q: Which of the following encapsulates PPP frames in Ethernet frames and uses common PPP features like authentication, encryption, and compression?

Correct answer: PPPoEPPPoE carries PPP frames inside Ethernet frames, which lets a provider keep PPP’s per-subscriber authentication, accounting, encryption and compression while delivering service over an Ethernet-style access network. It is the usual arrangement for DSL and fibre broadband, and PPPoA is its counterpart where the access link is ATM.

Q: The Acme Corporation is implementing dial-up services to enable remote-office employees to connect to the local network. The company uses multiple routed protocols, needs authentication of users connecting to the network, and since some calls will be long distance, needs callback support. Which of the following protocols is the best choice for these remote services?

Correct answer: PPPThree requirements point to PPP together: it carries multiple routed protocols over the same link, it authenticates with PAP or CHAP, and it supports callback, which is what turns a long-distance charge into one the company controls. HDLC in its Cisco form is proprietary and offers neither authentication nor multiprotocol negotiation, Frame Relay is not a dial-up technology, and 802.1 is not a WAN protocol at all.

Q: Which encapsulations can be configured on a serial interface? 1.Ethernet 2.Token Ring 3.HDLC 4.Frame Relay 5.PPP

Correct answer: 3, 4 and 5HDLC, Frame Relay and PPP are all serial encapsulations, and HDLC is the Cisco default. Ethernet and Token Ring are LAN technologies with their own interface types and cannot be configured on a serial line - the encapsulation must match the physical medium and the far end.

Q: Which command will display the CHAP authentication process as it occurs between two routers in the network?

Correct answer: debug ppp authenticationCHAP is an authentication method within PPP, so the debug that shows the exchange - the challenge, the response and the success or failure - is debug ppp authentication. There is no debug chap command, and show interface serial 0 reports the line and protocol state without showing the negotiation that produced it.

Q: Which of the following command options are displayed when you use the Router# show frame-relay ? command? 1.dlci 2.neighbors 3.lmi 4.pvc 5.map

Correct answer: 3, 4 and 5The question mark lists the available keywords, which are lmi, pvc and map - the local management interface statistics, the state and counters of each virtual circuit, and the mappings of protocol address to DLCI. There is no show frame-relay dlci or neighbors; the DLCI information appears within the pvc and map output.

11.

In which of the following technologies is the term HFC used?

A.DSL
B.PPPoE
C.Frame Relay
D.Cable

Answer: D

Correct answer: Cable

HFC stands for hybrid fibre-coaxial, the plant a cable operator uses: fibre from the head end to a neighbourhood node, then coaxial cable to the individual premises. It is specific to cable broadband. DSL runs over the existing telephone pair, and Frame Relay and a dedicated T1 are carrier services with no such plant of their own.

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12.

Which of the following encapsulates PPP frames in Ethernet frames and uses common PPP features like authentication, encryption, and compression?

A.PPP
B.PPPoA
C.PPPoE
D.Token Ring

Answer: C

Correct answer: PPPoE

PPPoE carries PPP frames inside Ethernet frames, which lets a provider keep PPP’s per-subscriber authentication, accounting, encryption and compression while delivering service over an Ethernet-style access network. It is the usual arrangement for DSL and fibre broadband, and PPPoA is its counterpart where the access link is ATM.

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13.

The Acme Corporation is implementing dial-up services to enable remote-office employees to connect to the local network. The company uses multiple routed protocols, needs authentication of users connecting to the network, and since some calls will be long distance, needs callback support. Which of the following protocols is the best choice for these remote services?

A.802.1
B.Frame Relay
C.HDLC
D.PPP
E.PPPoE

Answer: D

Correct answer: PPP

Three requirements point to PPP together: it carries multiple routed protocols over the same link, it authenticates with PAP or CHAP, and it supports callback, which is what turns a long-distance charge into one the company controls. HDLC in its Cisco form is proprietary and offers neither authentication nor multiprotocol negotiation, Frame Relay is not a dial-up technology, and 802.1 is not a WAN protocol at all.

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14.

When a router is connected to a Frame Relay WAN link using a serial DTE interface, how is the clock rate determined?

A.Supplied by the CSU/DSU
B.By the far end router
C.By the clock rate command
D.By the Physical layer bit stream timing

Answer: A

Clocking on a serial interface is always provided by the CSU/DSU (DCE device). However, if you do not have a CSU/DSU in your nonproduction test environment, then you need to supply clocking with the clock rate command on the serial interface of the router with the DCE cable attached.

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15.

Which encapsulations can be configured on a serial interface?

1.Ethernet

2.Token Ring

3.HDLC

4.Frame Relay

5.PPP

A.1 and 4
B.2 only
C.3, 4 and 5
D.All of the above

Answer: C

Correct answer: 3, 4 and 5

HDLC, Frame Relay and PPP are all serial encapsulations, and HDLC is the Cisco default. Ethernet and Token Ring are LAN technologies with their own interface types and cannot be configured on a serial line - the encapsulation must match the physical medium and the far end.

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16.

Which command will display the CHAP authentication process as it occurs between two routers in the network?

A.show chap authentication
B.show interface serial 0
C.debug ppp authentication
D.debug chap authentication

Answer: C

Correct answer: debug ppp authentication

CHAP is an authentication method within PPP, so the debug that shows the exchange - the challenge, the response and the success or failure - is debug ppp authentication. There is no debug chap command, and show interface serial 0 reports the line and protocol state without showing the negotiation that produced it.

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17.

Which of the following command options are displayed when you use the Router# show frame-relay ? command?

1.dlci

2.neighbors

3.lmi

4.pvc

5.map

A.1 only
B.2 and 4
C.3, 4 and 5
D.All of the above

Answer: C

Correct answer: 3, 4 and 5

The question mark lists the available keywords, which are lmi, pvc and map - the local management interface statistics, the state and counters of each virtual circuit, and the mappings of protocol address to DLCI. There is no show frame-relay dlci or neighbors; the DLCI information appears within the pvc and map output.

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18.

How should a router that is being used in a Frame Relay network be configured to keep split horizon issues from preventing routing updates?

A.Configure a separate subinterface for each PVC with a unique DLCI and subnet assigned to the subinterface.
B.Configure each Frame Relay circuit as a point-to-point line to support multicast and broadcast traffic.
C.Configure many subinterfaces in the same subnet.
D.Configure a single subinterface to establish multiple PVC connections to multiple remote router interfaces.

Answer: A

If you have a serial port configured with multiple DLCIs connected to multiple remote sites, split horizon rules, stop route updates received on an interface from being sent out the same interface. By creating subinterfaces for each PVC, you can avoid the split horizon issues when using Frame Relay.

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