How does PPP interface with different network layer protocols?
PPP can support multiple network layer protocols, such as IPv4, IPv6, IPX, and AppleTalk. It handles the interface with various network layer protocols via separate NCPs. There is a protocol field in a PPP frame to specify the network layer protocol that is being used. The information field in a PPP frame is the data payload. LCP sets up and terminates a link. It does not check which network layer protocol is used for the data.
A network engineer is monitoring an essential, but poor quality, PPP WAN link that periodically shuts down. An examination of the interface configurations shows that the ppp quality 90 command has been issued. What action could the engineer take to reduce the frequency with which the link shuts down?
Issuing the ppp quality 70 command will reduce the link quality threshold before it shuts down from 90% of packets received that were sent, to a drop rate of 70% before shutting down. Setting the threshold to 100% will shut down the link if 100% of packets are not received. Lowering the clock rate will not help a link that is going down. The bandwidth command is used for routing protocol calculations, not link quality.
Which is an advantage of using PPP on a serial link instead of HDLC?
Authentication, multilink, and compression are options on PPP that are advantages over HDLC.
In which situation would the use of PAP be preferable to the use of CHAP?
There are times when PAP should be used instead of CHAP. When a plain text password is needed to simulate login at a remote host, PAP is preferable, since passwords are not sent in clear text with CHAP.
Which three physical layer interfaces support PPP? (Choose three.)
PPP can operate across any DTE/DCE interface in either asynchronous or synchronous bit serial mode. The high-speed serial interface (HSSI) developed by Cisco Systems and T3 plus Networking is a DTE/DCE interface that provides high speed connectivity. Asynchronous serial interfaces and synchronous serial interfaces are also DTE/DCE interfaces.
Match the PPP options with the correct description. (Not all options are used.)
Which protocol will terminate the PPP link after the exchange of data is complete?
LCP terminates a link after exchange of data is complete by exchanging link-termination packets. The link may terminate for various reasons before the data exchange is complete. NCP will only terminate the network layer and NCP link. IPCP and IPXCP are specific network control protocols.
Which three are types of LCP frames used with PPP? (Choose three.)
Link-establishment frames establish and configure a link. Link-maintenance frames manage and debug a link. Link-termination frames terminate a link.
What are three components of PPP? (Choose three.)
PPP is a WAN protocol to provide serial point-to-point connections. The three main components of HDLC include the Network Control Protocol (NCP), an extensible Link Control Protocol (LCP), and framing similar to HDLC.
The exhibit has two boxes. The first box shows the following partial command output:
Refer to the exhibit. A network administrator is configuring the PPP link between the two routers. However, the PPP link cannot be established. Based on the partial output of the show running-config command, what is the cause of the problem?
In PPP authentication, the passwords are case sensitive and must match on both sides.
Which command can be used to view the cable type that is attached to a serial interface?
The show controllers command will allow an administrator to view the type of cable attached to a serial interface such as a V.35 DCE.
Which serial 0/0/0 interface state will be shown if no serial cable is attached to the router, but everything else has been correctly configured and turned on?
The show interfaces privileged exec mode command shows the state of the interfaces, along with much other information that related to them. “Serial 0/0/0 is down, line protocol is down” is displayed if there is no cable connected because there is no Layer 1 or Layer 2 activity going on. The interface has been turned on by the use of the no shutdown command, otherwise the “Serial 0/0/0 is administratively down, line protocol is down” message would be displayed, whether a cable has been connected or not.
Which two statements describe a PPP connection between two Cisco routers? (Choose two.)
PPP uses LCP to perform the functions of establishing, configuring, and testing the data-link connections on the link as well as negotiating encapsulation, authentication, and compression formats.
The exhibit displays some partial debug command output:
Refer to the exhibit. Based on the debug command output that is shown, which statement is true of the operation of PPP.
A laptop is connected to an AP and is associated with the connection that is labeled A. The AP is connected to a switch and is associated with the connection that is labeled B. A PC is attached to the switch. The switch is connected to router RTA. The connection of the PC, through the switch, to RTA is associated with the connection that is labeled C. RTA is connected via a serial connection to the ISP and is associated with the connection labeled D.
Refer to the exhibit. What type of Layer 2 encapsulation will be used for connection D on the basis of this configuration on a newly installed router:
HDLC is the default encapsulation method on Cisco router serial interfaces. If no other encapsulation is configured, the interface will default to HDLC.
How much total bandwidth is provided by a T1 line?
A T1 line consists of 24 voice channels with 64 kb/s each of bandwidth. This gives a T1 link a total bandwidth of 1.544 Mb/s.
Match the steps to the PPP CHAP authentication process sequence. (Not all options are used.)
Match the phases of establishing a PPP session in the correct order. (Not all options are used.)
Which PPP option can detect links that are in a looped-back condition?
A Magic Number is randomly generated by PPP at each end of the connection. This number is used by the devices at each end to detect a looped-back condition.
Which field marks the beginning and end of an HDLC frame?
An HDLC frame consists of six or more fields. Two Flag fields are used to mark the beginning and the end of the frame.
Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.
Why is the serial link between router R1 and router R2 not operational?
The hostname in one router must be the same as the username in the other router, unless a username is specified with the ppp pap sent-username interface command.
Which address is used in the Address field of a PPP frame?
Because PPP is point-to-point, it does not need to assign individual station addresses. The Address field in the frame is a single byte of binary sequence 11111111, the standard broadcast address.
A network engineer has issued the show interfaces serial 0/0/0 command on a router to examine the open NCPs on a PPP link to another router. The command output displays that the encapsulation is PPP and that the LCP is open. However, the IPV6CP NCP is not shown as open. What does the engineer need to configure to open the IPV6CP NCP on the link?
The PPP IPV6CP NCP will open when the interface on each router is configured with an IPv6 address.
When configuring Multilink PPP, where is the IP address for the multilink bundle configured?
When configuring a PPP multilink bundle, the IP address will be configured on the multilink interface, not on the physical interface. This is because the multilink bundle is representing two or more physical interfaces.
A network engineer is troubleshooting the loss of MPEG video viewing quality as MPEG video files cross a PPP WAN link. What could be causing this loss of quality?
Using the compress command when configuring PPP on interfaces can reduce the system performance due to a software compression process. The reduced performance may reduce the content delivery quality, especially in the case of audio and video streaming, such as MPEG file streaming. When compressed data files, such as .mpeg, .zip, and .tar files, are carried on the link, using the compress command is not recommended. If PAP is used but misconfigured, the PPP link will not work at all. The clock rate is needed only on the DCE side of a serial link. Configuring Link Quality Monitoring will only monitor the incoming and outgoing link quality. Link Quality Monitoring is not sensitive to which type of content is transmitted.