نمونه سوالات آزمون CCNA 200-120

نمونه سوالات آزمون CCNA Routing & Switching 200-120

Topic 8, WAN Technologies

QUESTION NO: 241

Refer to the exhibit:

In the Frame Relay network, which IP addresses would be assigned to the interfaces with point-topoint PVCs?

A. DLCI 16: 192.168.10.1 /24
DLCI 17: 192.168.10.1 /24
DLCI 99: 192.168.10.2 /24
DLCI 28: 192.168.10.3 /24

B. DLCI 16: 192.168.10.1 /24
DLCI 17: 192.168.11.1 /24
DLCI 99: 192.168.12.1 /24
DLCI 28: 192.168.13.1 /24

C. DLCI 16: 192.168.10.1 /24
DLCI 17: 192.168.11.1 /24
DLCI 99: 192.168.10.2 /24
DLCI 28: 192.168.11.2 /24

D. DLCI 16: 192.168.10.1 /24
DLCI 17: 192.168.10.2 /24
DLCI 99: 192.168.10.3 /24
DLCI 28: 192.168.10.4 /24

Answer: C
Explanation:

With point to point PVC, each connection needs to be in a separate subnet. The R2-R1 connection (DLCI 16 to 99) would have each router within the same subnet. Similarly, the R3-R1 connection would also be in the same subnet, but it must be in a different one than the R2-R1 connection.

QUESTION NO: 242

Which command is used to enable CHAP authentication, with PAP as the fallback method, on a serial interface?

A. Router(config-if)# ppp authentication chap fallback ppp
B. Router(config-if)# ppp authentication chap pap
C. Router(config-if)# authentication ppp chap fallback ppp
D. Router(config-if)# authentication ppp chap pap

Answer: B
Explanation:

This command tells the router to first use CHAP and then go to PAP if CHAP isn't available.

QUESTION NO: 243

Which protocol is an open standard protocol framework that is commonly used in VPNs, to provide secure end-to-end communications?

A. RSA
B. L2TP
C. IPsec
D. PPTP

Answer: C

Explanation:

IPSec is a framework of open standards that provides data confidentiality, data integrity, and data authentication between participating peers at the IP layer. IPSec can be used to protect one or more data flows between IPSec peers.

QUESTION NO: 244

At which layer of the OSI model does PPP perform?

A. Layer 2
B. Layer 3
C. Layer 4
D. Layer 5

Answer: A
Explanation:

The Point-to-Point Protocol (PPP) provides a standard method for transporting multi-protocol datagrams over point-to-point links. PPP was originally emerged as an encapsulation protocol for transporting IP traffic between two peers. It is a data link layer protocol (layer 2 in the OSI model)

QUESTION NO: 245

The command frame-relay map ip 10.121.16.8 102 broadcast was entered on the router. Which of the following statements is true concerning this command?

A. This command should be executed from the global configuration mode.
B. The IP address 10.121.16.8 is the local router port used to forward data.
C. 102 is the remote DLCI that will receive the information.
D. This command is required for all Frame Relay configurations.
E. The broadcast option allows packets, such as RIP updates, to be forwarded across the PVC.

Answer: E
Explanation:

Broadcast is added to the configurations of the frame relay, so the PVC supports broadcast, allowing the routing protocol updates that use the broadcast update mechanism to be forwarded across itself.

QUESTION NO: 246

Which two options are valid WAN connectivity methods? (Choose two.)

A. PPP
B. WAP
C. DSL
D. L2TPv3
E. Ethernet

Answer: A,C
Explanation:

QUESTION NO: 247

Which Layer 2 protocol encapsulation type supports synchronous and asynchronous circuits and has built-in security mechanisms?

A. HDLC
B. PPP
C. X.25
D. Frame Relay

Answer: B
Explanation:

PPP: Provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. PPP was designed to work with several network layer protocols, including IP. PPP also has built-in security mechanisms, such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).

QUESTION NO: 248

Which encapsulation type is a Frame Relay encapsulation type that is supported by Cisco routers?

A. IETF
B. ANSI Annex D
C. Q9333-A Annex A
D. HDLC

Answer: A
Explanation:

Cisco supports two Frame Relay encapsulation types: the Cisco encapsulation and the IETF Frame Relay encapsulation, which is in conformance with RFC 1490 and RFC 2427. The former is often used to connect two Cisco routers while the latter is used to connect a Cisco router to a non-Cisco router. You can test with your Cisco router when typing the command Router(config-if)# encapsulation frame-relay ? on a WAN link. Below is the output of this command (notice Cisco is the default encapsulation so it is not listed here, just press Enter to use it).

Note: Three LMI options are supported by Cisco routers are ansi, Cisco, and Q933a. They represent the ANSI Annex D, Cisco, and ITU Q933-A (Annex A) LMI types, respectively. HDLC is a WAN protocol same as Frame-Relay and PPP so it is not a Frame Relay encapsulation type.

QUESTION NO: 249

RouterA is unable to reach RouterB. Both routers are running IOS version 12.0.

After reviewing the command output and graphic, what is the most likely cause of the problem?

A. incorrect bandwidth configuration
B. incorrect LMI configuration
C. incorrect map statement
D. incorrect IP address

Answer: C
Explanation:

First we have to say this is an unclear question and it is wrong. The “frame-relay map ip” statement is correct thus none of the four answers above is correct. But we guess there is a typo in the output. Maybe the “ip address 172.16.100.2 255.255.0.0 command should be “ip address 172.16.100.1 255.255.0.0. That makes answer C correct.

QUESTION NO: 250

Refer to the exhibit.

What is the meaning of the term dynamic as displayed in the output of the show frame-relay map command shown?

A. The Serial0/0 interface is passing traffic.
B. The DLCI 100 was dynamically allocated by the router.
C. The Serial0/0 interface acquired the IP address of 172.16.3.1 from a DHCP server.
D. The DLCI 100 will be dynamically changed as required to adapt to changes in the Frame Relay cloud.
E. The mapping between DLCI 100 and the end station IP address 172.16.3.1 was learned through Inverse ARP.

Answer: E
Explanation:

Inverse Address Resolution Protocol (Inverse ARP) was developed to provide a mechanism for dynamic DLCI to Layer 3 address maps. Inverse ARP works much the same way Address Resolution Protocol (ARP) works on a LAN. However, with ARP, the device knows the Layer 3 IP address and needs to know the remote data link MAC address. With Inverse ARP, the router knows the Layer 2 address which is the DLCI, but needs to know the remote Layer 3 IP address. When using dynamic address mapping, Inverse ARP requests a next-hop protocol address for each active PVC. Once the requesting router receives an Inverse ARP response, it updates its DLCI-to-Layer 3 address mapping table. Dynamic address mapping is enabled by default for all protocols enabled on a physical interface. If the Frame Relay environment supports LMI autosensing and Inverse ARP, dynamic address mapping takes place automatically. Therefore, no static address mapping is required.

QUESTION NO: 251

A network administrator needs to configure a serial link between the main office and a remote location. The router at the remote office is a non-Cisco router. How should the network administrator configure the serial interface of the main office router to make the connection?

A. Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252
Main(config-if)# no shut

B. Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252
Main(config-if)# encapsulation ppp
Main(config-if)# no shut

C. Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252
Main(config-if)# encapsulation frame-relay
Main(config-if)# authentication chap
Main(config-if)# no shut

D. Main(config)# interface serial 0/0
Main(config-if)#ip address 172.16.1.1 255.255.255.252
Main(config-if)#encapsulation ietf
Main(config-if)# no shut

Answer: B
Explanation:

With serial point to point links there are two options for the encapsulation. The default, HDLC, is Cisco proprietary and works only with other Cisco routers. The other option is PPP which is standards based and supported by all vendors.

QUESTION NO: 252

What are three reasons that an organization with multiple branch offices and roaming users might implement a Cisco VPN solution instead of point-to-point WAN links? (Choose three.)

A. reduced cost
B. better throughput
C. broadband incompatibility
D. increased security
E. scalability
F. reduced latency

Answer: A,D,E
Explanation:

IPsec offer a number of advantages over point to point WAN links, particularly when multiple locations are involved. These include reduced cost, increased security since all traffic is encrypted, and increased scalability as s single WAN link can be used to connect to all locations in a VPN, where as a point to point link would need to be provisioned to each location.

QUESTION NO: 253

Which two statistics appear in show frame-relay map output? (Choose two.)

A. the number of BECN packets that are received by the router
B. the value of the local DLCI
C. the number of FECN packets that are received by the router
D. the status of the PVC that is configured on the router
E. the IP address of the local router

Answer: B,D

QUESTION NO: 254

Users have been complaining that their Frame Relay connection to the corporate site is very slow. The network administrator suspects that the link is overloaded.

Based on the partial output of the Router# show frame relay pvc command shown in the graphic, which output value indicates to the local router that traffic sent to the corporate site is experiencing congestion?

A. DLCI = 100
B. last time PVC status changed 00:25:40
C. in BECN packets 192
D. in FECN packets 147
E. in DE packets 0

Answer: C
Explanation:

If device A is sending data to device B across a Frame Relay infrastructure and one of the intermediate Frame Relay switches encounters congestion, congestion being full buffers, oversubscribed port, overloaded resources, etc, it will set the BECN bit on packets being returned to the sending device and the FECN bit on the packets being sent to the receiving device.

QUESTION NO: 255

Which command allows you to verify the encapsulation type (CISCO or IETF) for a Frame Relay link?

A. show frame-relay lmi
B. show frame-relay map
C. show frame-relay pvc
D. show interfaces serial

Answer: B
Explanation:

When connecting Cisco devices with non-Cisco devices, you must use IETF4 encapsulation on both devices. Check the encapsulation type on the Cisco device with the show frame-relay map exec command.

QUESTION NO: 256

It has become necessary to configure an existing serial interface to accept a second Frame Relay virtual circuit. Which of the following procedures are required to accomplish this task? (Choose three.)

A. Remove the IP address from the physical interface.
B. Encapsulate the physical interface with multipoint PPP.
C. Create the virtual interfaces with the interface command.
D. Configure each subinterface with its own IP address.
E. Disable split horizon to prevent routing loops between the subinterface networks.
F. Configure static Frame Relay map entries for each subinterface network.

Answer: A,C,D
Explanation:

For multiple PVC’s on a single interface, you must use subinterfaces, with each subinterface configured for each PVC. Each subinterface will then have its own IP address, and no IP address will be assigned to the main interface.

QUESTION NO: 257

What occurs on a Frame Relay network when the CIR is exceeded?

A. All TCP traffic is marked discard eligible.
B. All UDP traffic is marked discard eligible and a BECN is sent.
C. All TCP traffic is marked discard eligible and a BECN is sent.
D. All traffic exceeding the CIR is marked discard eligible.

Answer: D
Explanation:

Committed information rate (CIR): The minimum guaranteed data transfer rate agreed to by the Frame Relay switch. Frames that are sent in excess of the CIR are marked as discard eligible (DE) which means they can be dropped if the congestion occurs within the Frame Relay network. Note: In the Frame Relay frame format, there is a bit called Discard eligible (DE) bit that is used to identify frames that are first to be dropped when the CIR is exceeded.

QUESTION NO: 258

Which two statements about using the CHAP authentication mechanism in a PPP link are true? (Choose two.)

A. CHAP uses a two-way handshake.
B. CHAP uses a three-way handshake.
C. CHAP authentication periodically occurs after link establishment.
D. CHAP authentication passwords are sent in plaintext.
E. CHAP authentication is performed only upon link establishment.
F. CHAP has no protection from playback attacks.

Answer: B,C
Explanation:

CHAP is an authentication scheme used by Point to Point Protocol (PPP) servers to validate the identity of remote clients. CHAP periodically verifies the identity of the client by using a three-way handshake. This happens at the time of establishing the initial link (LCP), and may happen again at any time afterwards. The verification is based on a shared secret (such as the client user's password).

QUESTION NO: 259

Refer to the exhibit.

Which statement describes DLCI 17?

A. DLCI 17 describes the ISDN circuit between R2 and R3.
B. DLCI 17 describes a PVC on R2. It cannot be used on R3 or R1.
C. DLCI 17 is the Layer 2 address used by R2 to describe a PVC to R3.
D. DLCI 17 describes the dial-up circuit from R2 and R3 to the service provider.

Answer: C
Explanation:

DLCI-Data Link Connection Identifier Bits: The DLCI serves to identify the virtual connection so that the receiving end knows which information connection a frame belongs to. Note that this DLCI has only local significance. Frame Relay is strictly a Layer 2 protocol suite.

QUESTION NO: 260

What is the result of issuing the frame-relay map ip 192.168.1.2 202 broadcast command?

A. defines the destination IP address that is used in all broadcast packets on DCLI 202
B. defines the source IP address that is used in all broadcast packets on DCLI 202
C. defines the DLCI on which packets from the 192.168.1.2 IP address are received
D. defines the DLCI that is used for all packets that are sent to the 192.168.1.2 IP address