1.
Which two statements are true about time-division multiplexing (TDM)? (Choose two.)
Correct Answer(s)
B. Multiple channels can transmit over a single link.
C. Original data streams must be reconstructed at the destination.
Explanation
TDM allows multiple channels to transmit over a single link by dividing the link's bandwidth into time slots. Each channel is allocated a specific time slot within the frame to transmit its data. Additionally, the original data streams must be reconstructed at the destination because TDM separates the data into time slots and interleaves them, so the receiving end needs to reassemble the data streams in the correct order.
2.
What does the demarcation point represent in data communication physical circuits?
Correct Answer
C. pHysical point at which the public network ends and the private customer network begins
Explanation
The demarcation point represents the physical point at which the public network ends and the private customer network begins in data communication physical circuits. This is the point where the responsibility for the network shifts from the service provider to the customer. It is typically located at the customer premises and marks the boundary between the two networks.
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?
Correct Answer(s)
B. EIA/TIA 422 (RS-422)
D. EIA/TIA-612/613 (HSSI)
Explanation
The correct answer is EIA/TIA 422 (RS-422) and EIA/TIA-612/613 (HSSI). EIA/TIA 422 (RS-422) is a serial communications interface standard that provides high-speed connectivity between LANs. It is commonly found on high-end Cisco routers. EIA/TIA-612/613 (HSSI) is another serial communications interface standard that also provides high-speed connectivity and is commonly found on Cisco routers. Both standards support high data rates, making them suitable for connecting LANs at speeds of up to 52 Mbps.
4.
Why are serial connections preferred over parallel connections for long transmission lengths?
Correct Answer
C. Parallel connections are subject to clock skew and to crosstalk between wires.
Explanation
Parallel connections are subject to clock skew and crosstalk between wires. Clock skew refers to the difference in arrival times of signals in a parallel connection, which can lead to synchronization issues. Crosstalk occurs when signals from one wire interfere with signals on adjacent wires, causing errors in data transmission. These issues make parallel connections less reliable for long transmission lengths compared to serial connections.
5.
Which three statements are correct about HDLC encapsulation? (Choose three.)
Correct Answer(s)
D. HDLC implementation in Cisco routers is proprietary.
E. HDLC is the default serial interface encapsulation on Cisco routers.
F. HDLC uses frame delimiters to mark the beginnings and ends of frames.
Explanation
HDLC implementation in Cisco routers is proprietary means that Cisco routers use their own implementation of HDLC, which may not be compatible with other vendors' devices. HDLC is the default serial interface encapsulation on Cisco routers indicates that when a serial interface is configured on a Cisco router, HDLC is automatically used as the encapsulation method. HDLC uses frame delimiters to mark the beginnings and ends of frames means that HDLC uses specific characters to indicate the start and end of a frame, allowing the receiver to correctly interpret the data.
6.
Which three statements are true regarding LCP? (Choose three.)
Correct Answer(s)
A. It is responsible for negotiating link establishment.
D. It terminates the link upon user request or the expiration of an inactivity timer.
E. It can test the link to determine if link quality is sufficient to bring up the link.
Explanation
LCP (Link Control Protocol) is responsible for negotiating link establishment, meaning it handles the process of establishing a connection between two devices. It also terminates the link upon user request or when an inactivity timer expires, ensuring that the connection is closed when necessary. Additionally, LCP can test the link to determine if the link quality is sufficient to establish a connection, allowing it to assess whether the link is stable and reliable.
7.
Which two options can LCP negotiate? (Choose two.)
Correct Answer(s)
A. Link quality
B. Authentication
Explanation
LCP (Link Control Protocol) can negotiate link quality and authentication options. Link quality negotiation allows devices to determine the quality of the connection and adjust parameters accordingly. Authentication negotiation ensures that both devices can verify each other's identities before establishing a connection.
8.
Which PPP configuration option can be used to establish load balancing over the interfaces of a router?
Correct Answer
B. Multilink
Explanation
Multilink is the correct answer because it allows load balancing over the interfaces of a router. With multilink, multiple physical links are combined into a single logical link, increasing the overall bandwidth and enabling load balancing across the interfaces. This is achieved by distributing traffic across the available links, thereby optimizing the utilization of resources and improving network performance.
9.
What function do Network Control Protocols provide for a PPP connection
Correct Answer
E. To allow multiple Layer 3 protocols to operate over the same pHysical link
Explanation
Network Control Protocols (NCPs) provide the function of allowing multiple Layer 3 protocols to operate over the same physical link. This means that NCPs enable the transmission of different network protocols, such as IP, IPX, or AppleTalk, over a single PPP connection. By supporting multiple Layer 3 protocols, NCPs enhance the flexibility and efficiency of network communications, allowing different devices and networks to communicate seamlessly 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?
Correct Answer
B. 2
Explanation
Based on the exhibit, the output shows that there are two NCP (Network Control Protocol) sessions established on the Serial0/0 interface. The "NCP Open" line indicates the number of NCP sessions that have been successfully opened, which in this case is 2. Therefore, the correct answer is 2.
11.
Refer to the exhibit. Which statement is true about PPP operation?
Correct Answer
D. Both the link-establishment and network-layer pHase completed successfully.
Explanation
The given exhibit does not provide any information about the status of Layer 2. However, it does mention that LCP, IPCP, and CDPCP negotiations are in progress, indicating that the link-establishment phase is ongoing. Additionally, it does not mention that only the link-establishment phase has completed successfully, but rather states that both the link-establishment and network-layer phase have completed successfully. Therefore, the correct answer is that both the link-establishment and network-layer phase completed successfully.
12.
Which three statements correctly describe PPP authentication? (Choose three
Correct Answer(s)
A. PAP sends passwords in clear text.
E. CHAP uses a challenge/response that is based on the MD5 hash algorithm
F. CHAP uses repeated challenges for verification.
Explanation
PAP sends passwords in clear text, which means that the password is not encrypted and can be easily intercepted. CHAP uses a challenge/response that is based on the MD5 hash algorithm, which provides a more secure authentication process by encrypting the password. Additionally, CHAP uses repeated challenges for verification, ensuring that the connection remains secure throughout the session.
13.
Which authentication protocol can be spoofed to allow playback attacks?
Correct Answer
C. PAP
Explanation
PAP (Password Authentication Protocol) can be spoofed to allow playback attacks. PAP sends passwords in clear text, making it vulnerable to interception and replay attacks. In a playback attack, an attacker intercepts the authentication process and replays the captured data to gain unauthorized access. Since PAP does not use encryption or mutual authentication, it is susceptible to spoofing and unauthorized access.
14.
Refer to the exhibit. What statement is true regarding the output shown?
Correct Answer
D. Data is able to flow across this link.
Explanation
The output shown indicates that the LCP negotiation has been successful, which means that the link has been established and is ready to transmit data. The fact that the NCP negotiation is still in progress does not affect the ability of data to flow across the link. Therefore, the statement "Data is able to flow across this link" is true based on the given information.
15.
Refer to the exhibit. What statement is true regarding the output shown?
Correct Answer
C. One router has suggested PAP authentication, and the other has accepted
Explanation
authentication but suggested CHAP authentication.
16.
Refer to the exhibit. Which two statements are true regarding the output shown? Choose two.)
Correct Answer(s)
A. The router has agreed on IP parameters
B. The router has negotiated LCP successfully.
Explanation
The output shown indicates that the router has agreed on IP parameters because the line "IP address 192.168.1.1, subnet mask 255.255.255.0" confirms that the router has successfully negotiated an IP address and subnet mask. Additionally, the line "LCP is Open" indicates that the router has negotiated LCP (Link Control Protocol) successfully. Therefore, the correct statements are that the router has agreed on IP parameters and has negotiated LCP successfully.
17.
What advantage does PPP have over HDLC for serial communications?
Correct Answer
D. It supports authentication
Explanation
PPP has an advantage over HDLC for serial communications because it supports authentication. This means that PPP can verify the identity of the devices communicating over the serial connection, ensuring that only authorized devices are allowed to access the network. This adds an extra layer of security and helps prevent unauthorized access or data breaches. HDLC, on the other hand, does not have built-in authentication capabilities, making it less secure in comparison.
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.)
Correct Answer(s)
A. The remote CSU or DSU has failed.
C. A timing problem has occurred on the cable.
Explanation
If the interface is in DCE mode, the remote CSU or DSU failing could cause the indicated problem. The CSU (Channel Service Unit) or DSU (Data Service Unit) are responsible for providing clocking and synchronization signals in a serial connection. If either of these fail, it can result in communication issues. Additionally, a timing problem on the cable can also cause problems. Timing problems can occur if the clocking signals are not properly synchronized between the devices connected by the cable.
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?
Correct Answer
A. 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
Explanation
The correct answer is the second option:
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
This set of commands configures the DTE router (R3) to communicate over its serial 0/0/0 interface with the DCE router (R1) using PPP encapsulation with CHAP authentication. The hostname of the DTE router is set to R3, and a username/password pair is configured for the DCE router (R1). The serial interface is configured with the appropriate IP address and subnet mask, and PPP encapsulation is enabled. Finally, CHAP authentication is configured for the PPP connection.
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?
Correct Answer
E. The interface has been administratively shutdown with the shutdown command.
Explanation
The reason why Router R1 is not able to communicate with the neighbor router is because the interface connecting them has been administratively shutdown with the shutdown command. This means that the interface is intentionally disabled, preventing any communication through it.