CCNA 4, Chapter 2 Exam

A T1 line provides a total bandwidth of 1.544 Mb/s.

The field that marks the beginning and end of an HDLC frame is the Flag. The Flag field is a unique bit pattern that is used to delimit the start and end of each frame in HDLC communication. It consists of six consecutive 1 bits followed by a 0 bit. The Flag field helps in synchronizing the sender and receiver, allowing them to identify the boundaries of each frame and ensuring reliable data transmission.

The IP address for the multilink bundle is configured on a multilink interface. Multilink PPP allows multiple physical links to be combined into a single logical link, providing increased bandwidth and redundancy. The multilink interface acts as the endpoint for the combined links and is where the IP address is assigned. This allows the multilink bundle to function as a single interface with its own IP address, enabling routing and communication over the combined links. Configuring the IP address on the multilink interface ensures that the bundle is properly identified and can participate in network communication.

The command "Router(config)# show controllers" can be used to view the cable type that is attached to a serial interface. This command provides detailed information about the hardware controllers on the router, including the type of cable connected to each interface.

The address used in the Address field of a PPP frame is a single byte of binary 11111111. This address is known as the broadcast address, and it is used to send a frame to all devices on the network. Using this address ensures that the frame reaches every device connected to the PPP network.

The correct answer is to issue the command "ppp quality 70". This command will lower the acceptable quality threshold for the PPP link, allowing for a higher tolerance of poor quality. By setting the threshold to 70, the link will be less likely to shut down when experiencing occasional drops in quality.

PPP (Point-to-Point Protocol) is a data link protocol commonly used in establishing internet connections. The three components of PPP mentioned in the answer are LCP (Link Control Protocol), NCP (Network Control Protocol), and HDLC-like framing. LCP is responsible for establishing, configuring, and terminating the link between two devices. NCP is used for establishing and configuring different network layer protocols, such as IP or IPX. HDLC-like framing refers to the encapsulation of data in a frame format similar to HDLC (High-Level Data Link Control) protocol. These components collectively enable PPP to provide authentication, encryption, error detection, and other functionalities in point-to-point communication.

The Magic Number option in PPP can detect links that are in a looped-back condition. This option allows the sender to include a unique number in each PPP frame, and the receiver can check if the received number matches the expected number. If there is a looped-back condition, the received number will not match the expected number, indicating a problem in the link. This helps in detecting and resolving looped-back conditions in PPP connections.

To open the IPV6CP NCP on the link, the network engineer needs to configure an IPv6 address on each interface on the link. This is because the IPV6CP NCP is responsible for negotiating and establishing IPv6 addresses on the PPP link. By configuring an IPv6 address on each interface, the engineer enables the negotiation process for the IPV6CP NCP, allowing it to be shown as open in the command output of the show interfaces serial 0/0/0 command.

Based on the given configuration, the Layer 2 encapsulation used for connection D would be HDLC. This is because HDLC (High-Level Data Link Control) is a synchronous data link layer protocol that is commonly used for point-to-point serial connections. The configuration provided does not mention any specific Layer 2 encapsulation protocol, so the default protocol used by Cisco routers is HDLC. Therefore, HDLC would be the correct answer in this case.

LCP (Link Control Protocol) is responsible for establishing, configuring, and terminating the PPP (Point-to-Point Protocol) link between two devices. It manages the link and ensures that it is functioning properly. Once the exchange of data is complete, LCP will terminate the PPP link, closing the connection between the devices. NCP (Network Control Protocol) is responsible for establishing and configuring network-layer protocols, such as IP (Internet Protocol) or IPX (Internetwork Packet Exchange). IPCP (Internet Protocol Control Protocol) is a specific NCP used for IP, while IPXCP is used for IPX. However, neither NCP nor its specific implementations are responsible for terminating the PPP link.

If no serial cable is attached to the router, the interface will be in the "down" state. The "line protocol" refers to the status of the data link layer protocol, which is responsible for establishing and maintaining a link between devices. Since no cable is connected, the line protocol will also be in the "down" state. Therefore, the correct answer is "Serial 0/0/0 is down, line protocol is down."

The three physical layer interfaces that support PPP are synchronous serial, HSSI, and asynchronous serial. PPP (Point-to-Point Protocol) is a data link protocol commonly used for establishing a direct connection between two nodes. Synchronous serial, HSSI (High-Speed Serial Interface), and asynchronous serial are all types of physical interfaces that can be used to establish this connection and support PPP. FastEthernet, GigabitEthernet, and Ethernet are not physical layer interfaces that support PPP.

PPP interfaces with different network layer protocols by using separate NCPs. NCP stands for Network Control Protocol, which is responsible for establishing and configuring the network layer protocol over the PPP link. Each network layer protocol has its own NCP, which handles the negotiation and configuration of that specific protocol. This allows PPP to support multiple network layer protocols simultaneously, as each protocol can have its own NCP to handle its specific requirements.

PAP (Password Authentication Protocol) sends passwords in plain text, while CHAP (Challenge Handshake Authentication Protocol) uses a more secure method of authentication. However, in some situations where there is a need to simulate login at the remote host using plain text passwords, PAP would be preferable as it allows for this specific requirement.

Based on the partial output of the show running-config command, it can be inferred that the passwords configured on the two routers do not match. This is indicated by the presence of the "ppp authentication password" command with different passwords on each router. Since the passwords must match for the PPP link to be established, this is likely the cause of the problem.

PPP (Point-to-Point Protocol) offers the advantage of providing an option for authentication on a serial link. This means that PPP allows the verification of the identity of the devices communicating over the link, ensuring secure and authorized access. HDLC (High-Level Data Link Control) does not have this feature, making it less secure in terms of verifying the authenticity of the devices. Therefore, the option for authentication is an advantage of using PPP over HDLC on a serial link.

The given debug command output shows that a PPP session was successfully established. There is no indication of any authentication failure or attempts for both PAP and CHAP authentication. The debug output is specifically from router R2, which suggests that the PPP session on this particular router was successfully established.

The compress command was used when PPP was configured on the interfaces. This command enables data compression on the PPP link, which can cause loss of quality for MPEG video files. Data compression algorithms may remove or alter certain data in order to reduce the size of the file, resulting in a loss of video quality.

LCP (Link Control Protocol) is responsible for establishing, configuring, and testing the link between two Cisco routers in a PPP connection. It performs quality testing to ensure the link is stable and reliable. Additionally, LCP manages compression on the link, allowing for efficient data transmission by compressing the data before sending it over the link. Therefore, the two statements that accurately describe a PPP connection between two Cisco routers are that LCP tests the quality of the link and LCP manages compression on the link.

The three types of LCP frames used with PPP are link-maintenance frames, link-termination frames, and link-establishment frames. These frames are used to establish, maintain, and terminate the link between two PPP devices. Link-maintenance frames are used to keep the link active and ensure its proper functioning. Link-termination frames are used to gracefully terminate the link when it is no longer needed. Link-establishment frames are used to initiate the link and negotiate the parameters between the devices.

The serial link between router R1 and router R2 is not operational because in each case the expected username is not the same as the remote router hostname. This means that the authentication process is failing, as the routers are expecting a different username than what is being provided. Therefore, the connection cannot be established.