CCNA 4 Chapter 2 v5.1 + v6.0 Test Online 2018-2019

Hint

Link-establishment frames establish and configure a link. Link-maintenance frames manage and debug a link. Link-termination frames terminate a link.

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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.

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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.

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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.

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An HDLC frame consists of six or more fields. Two Flag fields are used to mark the beginning and the end of the frame.

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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.

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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.

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This debug output is from router R1 and shows that a PPP session was successfully established. Success can be verified by the line of output with CDPCP: State is open.

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In PPP authentication, the passwords are case sensitive and must match on both sides.

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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.

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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.

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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.

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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.

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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.

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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.

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The PPP IPV6CP NCP will open when the interface on each router is configured with an IPv6 address.

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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.

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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.

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HDLC is the default encapsulation method on Cisco router serial interfaces. If no other encapsulation is configured, the interface will default to HDLC.

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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.

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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.

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Compression, Increases the effective throughput on PPP connections by reducing the amount of data in the frame that must travel across the link.; Multilink, Provides load balancing over the router interfaces. Maximum Recieve Unit, The maximum of the PPP frame. Not used, Helps to ensure a reliable loop-free data ink layer. Authentication Protocol, The two choices are Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).

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The first two steps happen at Layers 1 and 2. Once the link is established and configured, link quality can be determined before layer 3 configuration takes place.

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Authentication, multilink, and compression are options on PPP that are advantages over HDLC.