CCNA WAN Chapter 2

Multilink is the correct answer because it allows load balancing over the interfaces of a router. By combining multiple physical interfaces into a single logical interface, multilink enables the distribution of traffic across these interfaces, thereby achieving load balancing. This helps in optimizing network performance and utilization by utilizing the available bandwidth of multiple links simultaneously.

The demarcation point in data communication physical circuits represents the physical point at which the public network ends and the private customer network begins. This is the point where the responsibility for the network switches from the service provider to the customer. It is typically located at the customer premises and is used to separate the public network infrastructure from the customer's private network.

The reason why Router R1 is not able to communicate with the neighbor router is that the interface has been administratively shutdown with the shutdown command. This means that the interface is intentionally disabled by an administrator, preventing any communication through that interface.

Parallel connections are subject to clock skew and crosstalk between wires. Clock skew refers to the difference in arrival time of signals in parallel wires, which can result in data corruption. Crosstalk occurs when signals from one wire interfere with signals on adjacent wires, leading to data errors. These issues become more prominent with longer transmission lengths, making serial connections a preferred choice as they minimize clock skew and crosstalk.

Based on the show interface Serial0/0 output, the NCP (Network Control Protocol) sessions are established between two devices. The exhibit does not provide any information about additional sessions beyond the two mentioned, so the correct answer is two.

The correct series of commands will allow router R3 to communicate over its serial 0/0/0 interface to router R1. First, the hostname is set to R3. Then, a username and password are configured for the authentication process, with the username set as R1 and the password set as Cisco. Next, the interface Serial 0/0/0 is configured with the encapsulation set to PPP. An IP address is assigned to the interface, followed by the command to enable CHAP authentication. This series of commands ensures that router R3 is properly configured to communicate with router R1 over the serial connection.

PPP has an advantage over HDLC for serial communications because it supports authentication. This means that PPP can verify the identity of the devices involved in the communication, ensuring a secure and trusted connection. Authentication helps prevent unauthorized access and protects the integrity of the data being transmitted. HDLC, on the other hand, does not have built-in authentication capabilities, making it less secure in comparison.

The exhibit is not provided, so it is difficult to give a specific explanation for the correct answer. However, based on the given options, the statement "Both the link-establishment and network-layer phase completed successfully" is true about PPP operation. This means that both the physical link between the devices and the network layer protocols have been successfully established and are operational.

PAP (Password Authentication Protocol) can be spoofed to allow playback attacks. PAP is a weak authentication protocol that sends passwords in clear text, making it vulnerable to interception and replay attacks. In a playback attack, an attacker intercepts and records the authentication process, then replays it later to gain unauthorized access. This can be done because PAP does not provide any means of verifying the freshness or authenticity of the authentication request.

PAP sends passwords in clear text, meaning that the password is not encrypted and can be easily intercepted. CHAP uses a challenge/response mechanism based on the MD5 hash algorithm, which provides a more secure authentication process. This ensures that the password is not sent in clear text and is protected. Additionally, CHAP uses repeated challenges for verification, where the authentication server sends multiple challenges to the client for further verification, enhancing security.

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The output shown indicates that LCP negotiation has been successful, which means that the link has been established and data is able to flow across this link. The fact that LCP and NCP are waiting for CHAP authentication to complete does not affect the ability of data to flow across the link.

LCP (Link Control Protocol) is responsible for establishing and configuring a data link connection between two devices. It can negotiate link quality, which refers to the reliability and performance of the link, and authentication, which involves verifying the identity of the devices involved in the connection. LCP does not negotiate dynamic flow control, compression and network layer address for IP, or connection-oriented or connectionless communication methods. Therefore, the correct options are link quality and authentication.

LCP, or Link Control Protocol, is responsible for negotiating the establishment of a link between two devices. It is also responsible for terminating the link either upon user request or when an inactivity timer expires. Additionally, LCP can test the link to determine if the link quality is sufficient to bring up the link.

The output indicates that one router has suggested PAP authentication and the other has accepted authentication but suggested CHAP authentication. This means that the routers are trying to negotiate the authentication method, with one router preferring PAP and the other preferring CHAP.

TDM allows multiple sources to transmit over a single channel by dividing the channel into time slots that are allocated to each source. This enables efficient use of the channel's bandwidth. Additionally, original data streams must be reconstructed at the destination because TDM splits the data into time slots and interleaves them, so the receiving end needs to reassemble the data in its original form.

Network Control Protocols (NCPs) provide the function of allowing multiple Layer 3 protocols to operate over the same physical link in a PPP connection. This means that different network protocols, such as IP, IPX, or AppleTalk, can be used simultaneously over a single PPP connection. NCPs handle the negotiation and configuration of these protocols, ensuring that each protocol can communicate effectively over the shared link. This allows for efficient and flexible network connectivity, as multiple protocols can coexist and operate independently over the same physical connection.

The three correct statements about HDLC encapsulation are:

1. HDLC implementation in Cisco routers is proprietary. This means that Cisco has developed its own version of HDLC for use in their routers, which may not be compatible with other vendors' equipment.

2. HDLC is the default serial interface encapsulation on Cisco routers. This means that when a serial interface is configured on a Cisco router, HDLC is automatically used as the encapsulation method unless another method is specified.

3. HDLC uses frame delimiters to mark the beginnings and ends of frames. Frame delimiters are special characters or bit patterns that are used to indicate the start and end of a frame in the HDLC protocol.

The given exhibit does not provide any information about encryption, authentication, or the use of the Predictor algorithm. However, it states that 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. Therefore, the correct answer is that 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.

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If the interface is in DCE mode, the remote CSU or DSU failing could cause the indicated problem. The CSU/DSU is responsible for connecting the router to the WAN circuit, so if it fails, the interface will not be able to establish a connection. Additionally, a timing problem on the cable could also cause the issue. Timing problems can occur when the clocking settings on the router and the CSU/DSU do not match, leading to synchronization issues and a failure to establish a connection.