CCNA PPP and Frame Relay Questions

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CCNA PPP and Frame Relay Questions

  1. 1. Chapter 11 True/False Indicate whether the statement is true or false.____ 1. Asynchronous serial connections are typically used with analog modems.____ 2. The benefit of multilink is that you can combine the bandwidth of two separate devices over one logical con- nection.____ 3. Compared with PAP, CHAP provides a much more simple authentication process.____ 4. Using authentication with PPP connections is mandatory.____ 5. The Frame Relay map can be built automatically or statically depending on the Frame Relay topology. Multiple Choice Identify the choice that best completes the statement or answers the question.____ 6. PPP is an Internet standard protocol defined in RFCs 2153 and ____. a. 1551 c. 2234 b. 1661 d. 2532____ 7. The ____ is used at the Data Link layer to establish, configure, and test the connection. a. NCP c. IPCP b. ATCP d. LCP____ 8. In a production environment, you can use the ____ command from interface configuration mode, which will automatically shut down that interface when looping is detected. a. off-looped-interface c. down-when-looped b. looped off d. off-when-lopped____ 9. ____ checks the reliability of the link by monitoring the number of errors, latency between requests, connec- tion retries, and connection failures on the PPP link. a. LQM c. CHAP b. PAP d. LCDI____ 10. Once you have completed configuring your PPP interface, you can verify the changes using the ____ com- mand. a. show ppp c. show connection b. show link d. show interface____ 11. ____ is a communications technique for sending data over high-speed digital connections operating at any- where from 56 Kbps to 44.736 Mbps or higher. a. Frame Relay c. Slip b. PPP d. DLCI____ 12. The Frame Relay switch is also called the ____. a. FRAP c. FRND b. PDN d. FRAD
  2. 2. ____ 13. Frame Relay separates each data stream into logical (software-maintained) connections called ____. a. logical circuits c. physical circuits b. virtual circuits d. connection circuits____ 14. LMI uses ____ packets (sent every 10 seconds by default) to verify the Frame Relay link and to ensure the flow of data. a. keepalive c. hello b. discover d. beam____ 15. In multipoint configurations, routers use the protocol ____ to send a query using the DLCI number to find a remote IP address. a. Inverse DNS c. Inverse PPP b. Inverse ARP d. PAP____ 16. The basic LMI type has three information elements: report type, keepalive, and ____. a. id frame c. PVC status b. PAP status d. authentication type____ 17. A(n) ____ implementation prevents routing update information received on one physical interface from being rebroadcast to other devices through that same physical interface. a. PVC c. SDLC b. keepalive d. split horizon____ 18. When the sum of the data arriving over all virtual circuits exceeds the access rate, the situation is called ____. a. undersubscription c. overrate b. oversubscription d. underrate____ 19. The Frame Relay ____ topology is like the bus LAN topology; nodes are simply strung along in a daisy- chained fashion. a. full mesh c. partial mesh b. star d. peer____ 20. The ____ is the most popular Frame Relay topology. a. full mesh c. star b. peer d. partial mesh____ 21. The ____ is the most expensive Frame Relay topology to implement because each router has a direct connec- tion to every other router. a. full mesh c. partial mesh b. star d. peer____ 22. The Frame Relay ____ topology allows redundancy for critical connections. a. star c. peer b. full mesh d. partial mesh____ 23. In Frame Relay, to configure a multipoint subinterface, you map it to multiple remote routers using the same subnet mask, but different ____ numbers. a. DLCI c. CHAP b. PPP d. LCI____ 24. The ____ command associates the DLCI numbers with a specific subinterface. a. frame-relay interface-number b. frame-relay dlci number c. frame-relay interface-dlci
  3. 3. d. interface-dlci number____ 25. You can check your Frame Relay configuration by using ____ commands. a. status c. check b. show d. dlci-interface____ 26. The most common show commands for monitoring Frame Relay operation are show interface, ____, show frame-relay map, and show frame-relay lmi. a. show frame-relay pvc c. show frame b. show frame-relay status d. show interface lmi Completion Complete each statement. 27. PPP, like many WAN technologies, is based on the ___________________________________ protocol. 28. The ______________________________ process modifies and enhances the default characteristics of a PPP connection. 29. The ITU-T was formerly known as the ____________________________________________________________, which is the primary international organization for fostering cooperative standards for telecommunications equipment and systems. 30. In Frame Relay connections, the network device that connects to the Frame Relay switch is known as a(n) ___________________________________. 31. Frame Relay connections identify virtual circuits by ___________________________________ numbers. Matching Match each item with a statement below: a. HSSI f. DLCI numbers b. NCPs g. Frame Relay map c. PPP h. Subinterfaces d. Frame relay i. Split horizon e. DCE____ 32. an encapsulation type for serial interface communications____ 33. a routing technique that reduces the chance of routing loops on a network____ 34. allow the simultaneous use of multiple Network layer protocols and are required for each protocol that uses PPP____ 35. a packet switching and encapsulation technology that functions at the Physical and Data Link layers of the OSI reference model____ 36. switching equipment supplied by a telecommunications provider that serves as a connection to the public data network (PDN)____ 37. virtual interfaces associated with a physical interface
  4. 4. ____ 38. a table in RAM that defines the remote interface to which a specific DLCI number is mapped____ 39. a type of serial device that was developed by Cisco and T3Plus Networking____ 40. map virtual circuits to layer 3 protocol addresses Short Answer 41. Compare PPP with SLIP. 42. What are the elements of the PPP frame? 43. What are the actions involved in the LCP link configuration process? 44. Explain the use of DLCI numbers in Frame Relay. 45. Briefly describe Local Management Interface (LMI). 46. What are the types of encapsulation supported by LMI in Cisco routers? 47. What are the performance parameters for a Frame Relay connection? 48. How is congestion handled in Frame Relay? 49. What are the components of the Cisco Frame Relay frame?
  5. 5. 50. Briefly describe the various Frame Relay topologies. Chapter 11 Answer Section TRUE/FALSE 1. ANS: T PTS: 1 REF: 302 2. ANS: T PTS: 1 REF: 305 3. ANS: F PTS: 1 REF: 306 4. ANS: F PTS: 1 REF: 306 5. ANS: T PTS: 1 REF: 310 MULTIPLE CHOICE 6. ANS: B PTS: 1 REF: 302 7. ANS: D PTS: 1 REF: 302 8. ANS: C PTS: 1 REF: 304-305 9. ANS: A PTS: 1 REF: 30510. ANS: D PTS: 1 REF: 30811. ANS: A PTS: 1 REF: 30812. ANS: C PTS: 1 REF: 31013. ANS: B PTS: 1 REF: 31014. ANS: A PTS: 1 REF: 31215. ANS: B PTS: 1 REF: 31216. ANS: C PTS: 1 REF: 31317. ANS: D PTS: 1 REF: 31418. ANS: B PTS: 1 REF: 31719. ANS: D PTS: 1 REF: 31820. ANS: C PTS: 1 REF: 31821. ANS: A PTS: 1 REF: 31922. ANS: D PTS: 1 REF: 31923. ANS: A PTS: 1 REF: 32124. ANS: C PTS: 1 REF: 322-32325. ANS: B PTS: 1 REF: 32426. ANS: A PTS: 1 REF: 324 COMPLETION27. ANS: High-Level Data Link Control (HDLC) High-Level Data Link Control HDLC PTS: 1 REF: 30328. ANS: LCP link configuration
  6. 6. PTS: 1 REF: 30529. ANS: Consultative Committee on International Telephony and Telegraphy (CCITT) Consultative Committee on International Telephony and Telegraphy CCITT PTS: 1 REF: 30830. ANS: Frame Relay access device (FRAD) Frame Relay access device FRAD PTS: 1 REF: 31031. ANS: Data Link Connection Identifier (DLCI) Data Link Connection Identifier DLCI PTS: 1 REF: 310 MATCHING32. ANS: C PTS: 1 REF: 30633. ANS: I PTS: 1 REF: 31434. ANS: B PTS: 1 REF: 30235. ANS: D PTS: 1 REF: 30836. ANS: E PTS: 1 REF: 30837. ANS: H PTS: 1 REF: 31138. ANS: G PTS: 1 REF: 31039. ANS: A PTS: 1 REF: 30240. ANS: F PTS: 1 REF: 310 SHORT ANSWER41. ANS: PPP is an Internet standard protocol defined in RFCs 2153 and 1661. The IETF defined PPP to provide point- to-point, router-to-router, host-to-router, and host-to-host connections. PPP is considered a peer technology based on its point-to-point physical configuration. It is commonly used over dial-up or leased lines to provide connections into IP networks. PPP also supports other Network layer protocols such as Novell IPX and Ap- pleTalk. Due to its flexibility, PPP is the most widely used WAN connection method today. Serial Line Internet Protocol (SLIP) was the predecessor to PPP; it only supports TCP/IP connections. In ad- dition, SLIP offers no encryption, compression, or error correction. It is an analog protocol limited to 56-Kbps transmission. PPP overcomes all of SLIP’s limitations. Other advantages offered by PPP are the capability to handle asynchronous as well as synchronous communication. PPP is also more efficient and supports more protocols and interfaces. PTS: 1 REF: 302
  7. 7. 42. ANS: The elements of the PPP frame are as follows: • Flag—Binary sequence 01111110, which indicates the beginning of the frame • Address—Binary sequence 11111111; because PPP is used to create a point-to-point connection, there is no need for PPP to assign an individual address for each host. • Control—Binary sequence 00000011, which indicates that the transmission of user data will not be se- quenced and is to be delivered over a connectionless link • Protocol—Two bytes used to identify the protocol that is encapsulated • LCP (or Data)—The LCP information and the data that has been encapsulated from the higher layers. The default size of this field is 1500 bytes, but PPP implementations can negotiate a larger size for this field. • Frame Check Sequence (FCS)—Two bytes by default, but can be as large as four bytes; uses a cyclical re- dundancy check (CRC) to verify the integrity of the frame and ensure that it was not corrupted during trans- mission • Flag—Binary sequence 01111110 that identifies the end of the data frame PTS: 1 REF: 30443. ANS: The LCP link configuration process includes the following actions: • Link establishment—PPP must open and configure the PPP connection before any data can be transferred over the link. • Authentication (optional)—CHAP or PAP can be used to verify the identity of the devices that are establish- ing the connection. • Link-quality determination (optional)—Checks the quality of the link and monitors its reliability • Network layer protocol configuration negotiation—Identifies the appropriate Network layer protocol for the connection; the devices negotiate to use a protocol that is common to both. • Link termination—When the call is complete, or the specifications defining the call are no longer met, the call is terminated. PTS: 1 REF: 30544. ANS: Frame Relay connections identify virtual circuits by Data Link Connection Identifier (DLCI) numbers. The DLCI (pronounced dell-see) numbers map virtual circuits to layer 3 protocol addresses. For example, a DLCI number associates an IP address with a specific virtual circuit. DLCI numbers do not specify a physical port and are not unique identifiers on the network; instead, they have only local significance, which means they are important only to the local router and Frame Relay switch. DLCI numbers are usually assigned by the Frame Relay provider and are most likely not the same on either side of the Frame Relay switch. This is what is meant by “local significance.” The provider, which is usually the telco, controls how the DLCI switching occurs. Because DLCIs have only local significance, any available number can be selected for each end of a PVC at the time of subscription. PTS: 1 REF: 31045. ANS: Frame relay engineers designed Local Management Interface (LMI) in 1990 to enhance standard Frame Re- lay. The LMI basically extended the functionality of Frame Relay by: • Making the DLCIs globally significant rather than locally significant • Creating a signaling mechanism between the router and the Frame Relay switch, which could report on the status of the link • Supporting multicasting PTS: 1 REF: 312
  8. 8. 46. ANS: Cisco routers, for example, support these types of LMI encapsulation: • cisco—This LMI type was originally defined by four companies: DEC, Nortel, StrataCom, and Cisco. It al- lows for 992 virtual circuit addresses and uses DLCI 1023 as a management circuit, which transfers link and DLCI status messages. This is the default LMI encapsulation type on Cisco routers. • ansi—ANSI standard T1.617 Annex-D provides for 976 virtual circuit addresses and uses DLCI 0 as the management circuit. • q933a—ITU-T Q.933 Annex A, similar to ANSI T1.617 Annex-D, uses DLCI 0 as a management circuit. PTS: 1 REF: 31347. ANS: When organizations contract Frame Relay services from a telecommunications provider such as MCI, Sprint, AT&T, or one of the Regional Bell Operating Companies (RBOCs), the contract specifies parameters by which the connection is expected to function. Terms that appear in the contract may include: • Access rate—The speed of the line, which indicates transfer rate. Common U.S. access rates are 56 Kps, 64 Kbps, and 128 Kbps, which are provided by Integrated Services Digital Network (ISDN) connections; and 1.544 Mbps, which is provided by T1 connections. Access rate is also known as the local access rate. • Committed Information Rate (CIR)—The minimum transfer rate that the Frame Relay customer negotiates with the Frame Relay service provider. The service provider agrees to always allow the customer to transfer information at no less than the transfer rate specified by the CIR. This is usually lower than the access rate be- cause the transfer rate may exceed the CIR during short bursts. • Committed Burst Size (CBS)—The maximum amount of data bits that the service provider agrees to trans- fer in a set time period under normal conditions. • Excess Burst Size (EBS)—The amount of excess traffic (over the CBS) that the network will attempt to transfer during a set time period. The network can discard EBS data, if necessary. • Oversubscription—When the sum of the data arriving over all virtual circuits exceeds the access rate, the sit- uation is called oversubscription. This can occur when the CIR is exceeded by burst traffic from the virtual circuits. oversubscription results in dropped packets. In such a case, the dropped packets must be retransmit- ted. PTS: 1 REF: 316-31748. ANS: Frame relay switches attempt to control congestion on the network. When the Frame Relay switch recognizes congestion, it sends a forward explicit congestion notification (FECN) message to the destination router. This message tells the router that congestion occurred on the virtual circuit. In addition, the switch sends a back- ward explicit congestion notification (BECN) message to the transmitting, or source, router. The router’s re- action to the BECN should be to reduce the amount of traffic it is sending. A network administrator can configure certain types of traffic at the router as discard eligible (DE). Thus, dur- ing times of congestion, the router can discard DE frames to provide a more reliable service to frames that are not discard eligible. DE lists can be configured on a Cisco router to identify the characteristics of frames eligi- ble for discard. These lists are created based on the protocol or the interface, as well as on other characteris- tics. PTS: 1 REF: 31749. ANS: The Frame Relay frame format has the following specific parts: • Flag—An eight-bit binary sequence (01111110) that indicates the start of the data frame • Address—Two to four bytes that contain several pieces of Frame Relay information
  9. 9. • Ethertype—Identifies the type of higher-layer protocol being encapsulated (IP, IPX, or AppleTalk); this data field is specific to the Cisco proprietary frame format • Data—A variable-length field that contains the information from the higher layers encapsulated in the Frame Relay frame • FCS—frame check sequence (FCS) or cyclical redundancy check (CRC), a mathematical computation placed at the end of the frame and used to ensure that the frame was not corrupted during transmission • Flag—An eight-bit binary sequence (01111110) that indicates the end of the data frame PTS: 1 REF: 317-31850. ANS: Frame relay can use many different WAN topologies: peer (point-to-point), star (hub and spoke), partial mesh, or full mesh physical topology. The peer topology is like the bus LAN topology; nodes are simply strung along in a daisychained fashion. Very often, only two routers will be connected. This is the simplest WAN topology, and is the least expensive and easiest to configure. The disadvantage to the peer WAN topology is that a failure between nodes will af- fect the WAN; there is no redundancy. The star is the most popular Frame Relay topology. One router func- tions as a central point, or hub, in a simple hierarchical configuration. All other devices are connected to the central router as spokes would connect to a hub. Typically the network administrator will configure the cen- tral router with a single interface that makes a multipoint connection to all other routers. The full mesh is the most expensive topology to implement because each router has a direct connection to ev- ery other router. While this offers the most redundancy, it is extremely expensive to implement. The partial mesh allows redundancy for critical connections while being less expensive than the full mesh. Essentially, any Frame Relay topology that is not a star or a full mesh is a partial mesh. PTS: 1 REF: 318-319

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