This document contains a chapter on PPP and Frame Relay with 25 multiple choice questions, 11 true/false statements, and 15 completion, matching, and short answer questions. The questions cover topics such as PPP frame elements, LCP configuration process, use of DLCI numbers in Frame Relay, Local Management Interface, Frame Relay encapsulation types, Frame Relay topologies, and commands to verify Frame Relay configurations.

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. ____ 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. 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. ____ 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. 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: 305
10. ANS: D PTS: 1 REF: 308
11. ANS: A PTS: 1 REF: 308
12. ANS: C PTS: 1 REF: 310
13. ANS: B PTS: 1 REF: 310
14. ANS: A PTS: 1 REF: 312
15. ANS: B PTS: 1 REF: 312
16. ANS: C PTS: 1 REF: 313
17. ANS: D PTS: 1 REF: 314
18. ANS: B PTS: 1 REF: 317
19. ANS: D PTS: 1 REF: 318
20. ANS: C PTS: 1 REF: 318
21. ANS: A PTS: 1 REF: 319
22. ANS: D PTS: 1 REF: 319
23. ANS: A PTS: 1 REF: 321
24. ANS: C PTS: 1 REF: 322-323
25. ANS: B PTS: 1 REF: 324
26. ANS: A PTS: 1 REF: 324
COMPLETION
27. ANS:
High-Level Data Link Control (HDLC)
High-Level Data Link Control
HDLC
PTS: 1 REF: 303
28. ANS: LCP link configuration

6. PTS: 1 REF: 305
29. ANS:
Consultative Committee on International Telephony and Telegraphy (CCITT)
Consultative Committee on International Telephony and Telegraphy
CCITT
PTS: 1 REF: 308
30. ANS:
Frame Relay access device (FRAD)
Frame Relay access device
FRAD
PTS: 1 REF: 310
31. ANS:
Data Link Connection Identifier (DLCI)
Data Link Connection Identifier
DLCI
PTS: 1 REF: 310
MATCHING
32. ANS: C PTS: 1 REF: 306
33. ANS: I PTS: 1 REF: 314
34. ANS: B PTS: 1 REF: 302
35. ANS: D PTS: 1 REF: 308
36. ANS: E PTS: 1 REF: 308
37. ANS: H PTS: 1 REF: 311
38. ANS: G PTS: 1 REF: 310
39. ANS: A PTS: 1 REF: 302
40. ANS: F PTS: 1 REF: 310
SHORT ANSWER
41. 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. 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: 304
43. 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: 305
44. 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: 310
45. 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. 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: 313
47. 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: 316-317
48. 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: 317
49. 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. • 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: 317-318
50. 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