Chapter 10. ISDN

1:	What is the data transfer rate for an ISDN bearer channel? A. 12Kbps B. 16Kbps C. 56Kbps D. 64Kbps E. 128Kbps
2:	What is the data transfer rate for a BRI ISDN delta channel? A. 12Kbps B. 16Kbps C. 56Kbps D. 64Kbps E. 128Kbps
3:	Which protocol recommends telephone network standards for ISDN? A. A-series B. E-series C. I-series D. Q-series
4:	Which protocol deals with concepts, terminology, and methods? A. A-series B. E-series C. I-series D. Q-series
5:	Which protocol covers switching and signaling in ISDN? A. A-series B. E-series C. I-series D. Q-series
6:	How many bearer channels are provided in BRI? A. 1 B. 2 C. 16 D. 23
7:	How many bearer channels are provided in PRI for North America? A. 1 B. 2 C. 16 D. 23
8:	What is the data transfer rate for a PRI ISDN delta channel? A. 12Kbps B. 16Kbps C. 56Kbps D. 64Kbps E. 128Kbps
9:	How many bearer channels are provided in PRI for Europe? A. 16 B. 24 C. 30 D. 32
10:	Which channel provides setup, signaling, and termination in ISDN? A. B channel B. D channel C. S channel D. T channel
11:	Which channel in ISDN is used for the transfer of data and the bulk of network traffic? A. B channel B. D channel C. S channel D. T channel
12:	Which of the following designates a router or ISDN telephone as a device having a native ISDN interface? A. TE1 B. NT-2 C. NT-1 D. TE2 E. TA
13:	Which of the following is the point at which all ISDN lines at a customer site are aggregated and switched using a customer-switching device? A. TE1 B. NT-2 C. NT-1 D. TE2 E. TA
14:	Which of the following converts the four-wire BRI signals from an S/T interface into two-wire signals of a U interface? A. TE1 B. NT-2 C. NT-1 D. TE2 E. TA
15:	Which of the following designates a device such as a PC or router requiring a TA to adapt communication for BRI signals? A. TE1 B. NT-2 C. NT-1 D. TE2
16:	Which of the following converts EIA/TIA-232, V.35, and other signals into BRI signals? A. TE1 B. NT-2 C. NT-1 D. TE2 E. TA
17:	Which of the following reference points refers to the connection between a non–ISDN-compatible device and a terminal adapter? A. R B. S C. T D. U
18:	Which of the following reference points refers to the point that connects into the NT-2, or customer-switching device? A. R B. S C. T D. U
19:	Which of the following reference points refers to the outbound connection from the NT-2 to the ISDN network? A. R B. S C. T D. U
20:	Which of the following reference points refers to the connection between the NT-1 and the ISDN network owned by the telephone company? A. R B. S C. T D. U
21:	Which of the following components is supplied by the end user in the United States and by the provider in Europe? A. TE1 B. NT-2 C. NT-1 D. TE2 E. TA
22:	Which of the following designations indicates that the NT-1 is built in? A. TE1 B. NT-2 C. S/T D. U E. TA
23:	Which of the following is a series of characters that identifies you to the switch at the central office? A. UID B. SID C. SPID D. Terminal ID
24:	You need to specify the type of ISDN switch you are using to configure ISDN BRI. You are using a National ISDN-1. Which command is correct? A. switch-type ni1 B. switch-type basic-ni1 C. isdn switch-type ni1 D. isdn switch-type basic-ni1
25:	You have configured the switch type; however, your ISDN BRI connection is not working. What else should you do? A. Re-enter the switch type. B. Reload the router configuration. C. Restart the router. D. Flush NVRAM.
26:	You've set the switch type to AT&T 5ESS for your BRI connection. Your provider has given you your SPID. What is your next step? A. Configure only the SPID on the first B channel. B. Configure only the SPID on the second B channel. C. Configure the SPID on both B channels. D. Configure the SPID on neither B channel.
27:	You need to configure the SPID for your router. What command is appropriate? A. isdn spid1 spid-number B. isdn spid spid-number C. spid spid-number D. spid1 spid-number
28:	You are reviewing your device's current configuration. You notice that you have configured different switch type settings for your switch in both Global Configuration mode and Interface Configuration mode. What is the effective switch type? A. The global setting overrides all settings. B. The interface setting overrides the global setting for that interface. C. Neither setting takes effect. D. This configuration cannot be created.
29:	You have a T1 interface that needs to have ISDN PRI configured on all 24 channels. After you set the switch type and controller, what command should you enter next? A. pri-group timeslots 1-24 B. pri-group timeslots 0-23 C. timeslots 0-23 D. timeslots 1-24
30:	You type the following configuration into a router: access-list 110 permit tcp any any eq www dialer-list 1 protocol ip list 110 isdn switch-type basic-5ess interface bri0 ip address 10.0.0.1 255.0.0.0 dialer-group 1 dialer map ip 10.0.0.2 5551111 isdn spid1 55511110101 5551111 Next, you test the ISDN connection by attempting to send HTTP traffic. The line comes up successfully, and the HTTP traffic is transmitted across the ISDN connection. You then send SMTP traffic and notice that SMTP traffic is also being permitted. Why is SMTP traffic going across the ISDN connection? A. The access list is configured wrong. B. The dialer list is not applied correctly. C. The dialer-list command specifies only what traffic brings up the ISDN connection, not what traffic is allowed across after the connection is up. D. SMTP traffic is a subset of HTTP; therefore, it is allowed across the ISDN connection.
31:	You want to display statistics for the BRI interface configured on the router. What command should you enter? A. show isdn statistics B. show isdn bri C. show interfaces bri0 D. show isdn status
32:	You want to ensure the router is communicating properly with the switch by viewing the status of both Layer 1 and Layer 2, as well as by viewing the number of active calls. What command permits this? A. show isdn layers B. display isdn layers C. show isdn status D. show isdn info
33:	You need to examine Layer 2 messages regarding the D channel. Which command displays this information? A. debug isdn q921 B. debug show isdn C. show isdn layer2 D. show isdn q921
34:	You need to view Layer 3 messages regarding the setup and teardown of the ISDN network connection. Which command is appropriate? A. show isdn q931 B. show isdn layer3 C. debug isdn q931 D. debug isdn layer3
35:	You want to view CHAP and PAP information for your ISDN connection. Which command shows you the packet exchange information? A. debug isdn authentication B. debug ppp authentication C. debug authentication D. show isdn ppp
36:	You enter the following configuration into a router, but when you test it, you are unable to initiate the ISDN call. What is wrong? Router#config terminal Router(config)#hostname Arizona Arizona(config)#router rip Arizona(config-router)#network 10.0.0.0 Arizona(config-router)#network 192.168.200.0 Arizona(config-router)#version 2 Arizona(config-router)# no auto-summary Arizona(config-router)#passive-interface default Arizona(config-router)# no passive-interface eth0 Arizona(config-router)#exit Arizona(config)#interface ethernet0 Arizona(config-if)#ip address 10.0.0.1 255.0.0.0 Arizona(config-if)#interface bri0 Arizona(config-if)#ip address 192.168.200.93 255.255.255.252 Arizona(config-if)#encapsulation ppp Arizona(config-if)#ppp authentication chap Arizona(config-if)#dialer map ip 192.168.200.94 name Indiana 5553333 Arizona(config-if)# isdn spid1 55511110101 5551111 Arizona(config-if)#isdn spid2 55522220101 5552222 Arizona(config-if)# dialer-group 40 Arizona(config-if)#dialer idle-timeout 30 Arizona(config-if)#isdn switch-type basic-ni Arizona(config-if)#exit Arizona(config)#ip route 192.168.200.96 255.255.255.224 192.168.200.94 Arizona(config)#dialer-list 4 protocol ip permit Arizona(config)#username Indiana password sanjose A. The dialer group is applied wrong. B. The RIP configuration is wrong. C. The PPP authentication is configured wrong. D. The dialer map is configured wrong. E. The configuration is incomplete.
37:	You want to monitor PPP traffic and exchanges, including Link Control Protocol and Network Control Protocol. What command shows this information? A. debug ppp traffic B. show ppp traffic C. debug ppp negotiation D. show ppp negotiation
38:	Dial-on-demand routing (DDR) is designed for which of the following types of connections? A. Low-volume periodic connections B. High-volume periodic connections C. Low-volume persistent connections D. High-volume persistent connections
39:	In DDR operation, what is "interesting traffic"? A. Traffic signaling a possible attack B. Traffic that should be blocked C. Traffic that should initiate the connection D. Traffic that initiates from the router
40:	Which command allows you to specify interesting traffic for DDR? A. dialer-list B. accesslist C. dial list D. dial-list
41:	What command associates a port with a dial list? A. dialer-group B. dial port C. dialer port D. dialer-port
42:	What command associates a dialer string with a dial list? A. dialer-map B. dialer-list C. dial map D. dial list
43:	What three things are necessary to complete a DDR ISDN call? (Choose three.) A. Static routes B. Dialer information C. Interesting traffic D. Routing protocols E. SPID numbers F. DLCIs
44:	You've configured static routes for use with your DDR connection. You want to review the routes the router is using. What command displays these routes? A. show ip static B. show ip route C. show route D. show route static
45:	What BRI command displays statistics for the ISDN DDR call, including the source and destination information for the packet initiating the call? A. show ddr B. show dialer interface bri0 C. show dialer interface D. show interface bri0
46:	Which command allows you to receive debugging information about the packets received on a dialer interface? A. debug packets B. debug dialer C. debug interface D. debug dialer interface
47:	You need to disable the interface. Disconnecting any call in progress is acceptable. What command should you issue? A. no isdn B. shutdown isdn C. disable isdn D. shutdown
48:	You need to configure the line to disconnect if it has been idle for two minutes. What command should you use? A. dialer timeout 120 B. dialer idle-timeout 120 C. dialer idle 120 D. dialer line idle 120
49:	You have set the dialer load threshold value to 25. What is the minimum percentage load that will cause the line to initiate another call to the destination? A. 2.5% B. 10% C. 25% D. 100%
50:	Which of the following types of traffic are acceptable for ISDN BRI bearer channels? (Choose three.) A. Voice B. Data C. Signaling D. Acknowledgments E. Video

Answers and Explanations

A1:	Answer: D. The transfer rate of the bearer channel is 64Kbps. A, B, C, and E all feature incorrect bearer channel transfer rates.
A2:	Answer: B. The transfer rate for the delta channel is 16Kbps. A, C, D, and E all feature incorrect delta channel transfer rates.
A3:	Answer: B. The E-series specifies telephone network standards. A is incorrect because this is not a valid specification. C is incorrect, as the I-series specifies concepts, terminology, and methods for ISDN. D is incorrect, as the Q-series specifies switching and signaling in ISDN.
A4:	Answer: C. The I-series specifies concepts, terminology, and methods for ISDN. A is incorrect because this is not a valid specification. B is incorrect because the E-series specifies telephone network standards. D is incorrect, as the Q-series specifies switching and signaling in ISDN.
A5:	Answer: D. The Q-series specifies switching and signaling in ISDN. A is incorrect because this is not a valid specification. B is incorrect because the E-series specifies telephone network standards. C is incorrect because the I-series specifies concepts, terminology, and methods for ISDN.
A6:	Answer: B. There are only two bearer channels in BRI. A, C, and D all feature the incorrect number of bearer channels in BRI.
A7:	Answer: D. There are 23 bearer channels in PRI for North America as well as 1 delta channel. A, B, and C all feature the incorrect number of bearer channels.
A8:	Answer: D. The PRI D channel has a 64Kbps transfer rate to handle the larger number of bearer channels. Each bearer channel also has a 64Kbps transfer rate. A, B, C, and E all feature incorrect transfer rates.
A9:	Answer: C. There are 30 bearer channels in Europe for PRI. A, B, and D all feature the incorrect number of bearer channels for Europe.
A10:	Answer: B. This is provided by the D channel in ISDN. A is incorrect because the bearer channel carries data. C and D are not valid ISDN channels.
A11:	Answer: A. The bearer channel carries the bulk of network traffic and data. B is incorrect, as this is provided by the D channel in ISDN. C and D are not valid ISDN channels.
A12:	Answer: A. TE1 designates a router or ISDN telephone as a device having a native ISDN interface. B is incorrect because NT-2 indicates the point at which all ISDN lines at a customer site are aggregated and switched. C is incorrect because NT-1 converts the four-wire BRI signals from an S/T interface into the two-wire signals of a U interface. D is incorrect because TE2 is a device such as a PC or router that requires a TA to adapt communication for BRI signals. E is incorrect, as the TA converts EIA/TIA-232 and other signals into BRI signals.
A13:	Answer: B. NT-2 indicates the point at which all ISDN lines at a customer site are aggregated and switched. A is incorrect because TE1 designates a router or ISDN telephone as a device having a native ISDN interface. C is incorrect, as NT-1 converts the four-wire BRI signals from an S/T interface into the two-wire signals of a U interface. D is incorrect, as TE2 is a device such as a PC or router that requires a TA to adapt communication for BRI signals. E is incorrect because the TA converts EIA/TIA-232 and other signals into BRI signals.
A14:	Answer: C. NT-1 converts the four-wire BRI signals from an S/T interface into the two-wire signals of a U interface. A is incorrect because TE1 designates a router or ISDN telephone as a device having a native ISDN interface. B is incorrect because NT-2 indicates the point at which all ISDN lines at a customer site are aggregated and switched. D is incorrect, as TE2 is a device such as a PC or router that requires a TA to adapt communication for BRI signals. E is incorrect because the TA converts EIA/TIA-232 and other signals into BRI signals.
A15:	Answer: D. TE2 is a device such as a PC or router that requires a TA to adapt communication for BRI signals. A is incorrect because TE1 designates a router or ISDN telephone as a device having a native ISDN interface. B is incorrect because NT-2 indicates the point at which all ISDN lines at a customer site are aggregated and switched. C is incorrect because NT-1 converts the four-wire BRI signals from an S/T interface into the two-wire signals of a U interface.
A16:	Answer: E. The TA converts EIA/TIA-232 and other signals into BRI signals. A is incorrect because TE1 designates a router or ISDN telephone as a device having a native ISDN interface. B is incorrect because NT-2 indicates the point at which all ISDN lines at a customer site are aggregated and switched. C is incorrect, as NT-1 converts the four-wire BRI signals from an S/T interface into the two-wire signals of a U interface. D is incorrect because TE2 is a device such as a PC or router that requires a TA to adapt communication for BRI signals.
A17:	Answer: A. The R reference point refers to the connection between a non–ISDN-compatible device and a terminal adapter. B is incorrect because S refers to the point that connects into the NT-2 or customer-switching device. C is incorrect because the T reference point refers to the outbound connection from the NT-2 to the ISDN network. D is incorrect; this refers to the connection between the NT-1 and ISDN network owned by the telephone company.
A18:	Answer: B. S refers to the point that connects into the NT-2 or customer-switching device. A is incorrect because the R reference point refers to the connection between a non–ISDN-compatible device and a terminal adapter. C is incorrect because the T reference point refers to the outbound connection from the NT-2 to the ISDN network. D is incorrect; this refers to the connection between the NT-1 and ISDN network owned by the telephone company.
A19:	Answer: C. The T reference point refers to the outbound connection from the NT-2 to the ISDN network. A is incorrect because the R reference point refers to the connection between a non–ISDN-compatible device and a terminal adapter. B is incorrect, as S refers to the point that connects into the NT-2 or customer-switching device. D is incorrect; this refers to the connection between the NT-1 and ISDN network owned by the telephone company.
A20:	Answer: D. This reference point refers to the connection between the NT-1 and ISDN network owned by the telephone company. A is incorrect because the R reference point refers to the connection between a non–ISDN-compatible device and a terminal adapter. B is incorrect, as S refers to the point that connects into the NT-2 or customer-switching device. C is incorrect because the T reference point refers to the outbound connection from the NT-2 to the ISDN network.
A21:	Answer: C. The NT-1 is supplied by the end user in the United States and by the provider in Europe. A, B, and D are not correct because they are all end-user devices.
A22:	Answer: D. U indicates that the NT-1 is built in. C is incorrect, as this indicates the NT-1 is not built in. A, B, and E are all incorrect, as they have no bearing on the NT-1.
A23:	Answer: C. This is the service profile identifier (SPID) assigned by the provider. D is incorrect, as the terminal ID is not a designation assigned by the ISDN provider. A and B are not valid ISDN acronyms.
A24:	Answer: D. the correct format to specify a national ISDN-1 switch is isdn switch-type basic-ni1. B is incorrect because this is not the proper syntax. A and C use invalid syntax.
A25:	Answer: C. Setting the switch type requires a router reboot to take effect. A is incorrect, as this is not the most likely problem. B is incorrect because reloading the router configuration does not force the setting to take effect. D is incorrect, as this problem is not indicative of an NVRAM problem.
A26:	Answer: D. The 5ESS switch does not require you to configure the SPID. A and B are incorrect, as these are rarely the proper configurations. Typically, both channels are configured, or neither channel is configured. C is incorrect because this is not valid for this switch type.
A27:	Answer: A. This is the proper syntax to configure the SPID. B is incorrect, as you need to specify spid1 or spid2, for instance. C and D are incorrect because isdn should precede the command.
A28:	Answer: B. An interface setting overrides the global setting. A is incorrect because you can override the global setting at the interface level. C is incorrect because both settings are effective. D is incorrect, as this is a valid configuration.
A29:	Answer: A. The proper syntax is pri-group timeslots 1-24. B is incorrect, as the values are 1–24, not 0–23. C is incorrect because the values are wrong, and the pri-group command precedes the timeslots keyword. D is incorrect because the pri-group command has been left out.
A30:	Answer: C. The dialer list in the configuration references access list 110. Access list 110 causes any HTTP traffic to bring up the ISDN connection. This access list is not used as a packet filter, however; so after the ISDN line is up, all traffic (including non-HTTP traffic) is allowed across the link. A and B are incorrect because the configuration is configured correctly. D is incorrect because SMTP is not a subset of HTTP.
A31:	Answer: C. The proper command is show interfaces bri0. D is incorrect, as this does not show the requested information. A and B are invalid IOS commands.
A32:	Answer: C. The show isdn status command displays Layer 1 status and Layer 2 status information. A, B, and D are all invalid IOS commands.
A33:	Answer: A. The debug isdn q921 command shows Layer 2 information for the D channel. B, C, and D are all invalid IOS commands.
A34:	Answer: C. The debug isdn q931 command is the correct command to view Layer 3 debugging information. A, B, and D are invalid IOS commands.
A35:	Answer: B. The debug ppp authentication command allows you to view authentication protocol information, such as that from CHAP and PAP. D is incorrect, as it does not show the requested information. A and C are not valid IOS commands.
A36:	Answer: A. The dialer list is 4 but is applied as number 40. B, C, and D are incorrect because there is nothing wrong with the remaining configuration. E is incorrect because the configuration is complete.
A37:	Answer: C. The debug ppp negotiation command shows PPP traffic exchanges and negotiation information, including LCP and NCP information. A, B, and D are all invalid IOS commands.
A38:	Answer: A. DDR is ideal for low-volume periodic connections and can help keep costs down when cost is tied to the amount of bandwidth used. B is incorrect because high-volume connections can be better served with a persistent high-bandwidth connection. C is incorrect, as persistent connections don't require DDR. D is incorrect because high-volume persistent connections are not served well by DDR.
A39:	Answer: C. Interesting traffic activates the link, causing it to connect and the traffic to be delivered. A is incorrect because this is not interesting traffic as defined by DDR. B is incorrect because interesting traffic should be delivered, not blocked. D is incorrect because interesting traffic does not necessarily initiate at the router.
A40:	Answer: A. The dialer-list command is used to specify interesting traffic by applying an access list to an interface. C is incorrect, as this is not the appropriate command. B and D are invalid IOS commands.
A41:	Answer: A. You use the dialer-group command to associate a port with a dial list. B, C, and D are all invalid IOS commands.
A42:	Answer: A. To associate a dialer string with a dial list, you use the dialer-map command. B is incorrect because this is not the correct command. C and D are both invalid IOS commands.
A43:	Answers: A, B, and C. You must have a static route, you must have dialer information to call the opposite-side router, and you must specify what interesting traffic will initiate the call. D is incorrect, as dynamic routing protocols can cause issues with dial-on-demand routing. E is incorrect because SPIDs are optional and not all switch types or service providers require them. F is incorrect, as Data-link connection identifiers (DLCIs) are used by frame relay to identify virtual circuits.
A44:	Answer: B. The show ip route command shows the static and dynamic routes on the router. C is incorrect, as this is not the appropriate command. A and D are invalid IOS commands.
A45:	Answer: B. The correct command to display statistics is show dialer interface bri0. C is incorrect because it's an incomplete IOS command. A and D are both invalid IOS commands.
A46:	Answer: B. The debug dialer command displays debugging information for the packets on a dialer interface. A and D are invalid IOS commands. C is incorrect; although this is a valid command, it does not show the requested information.
A47:	Answer: D. You use the shutdown command on the interface to disable it. A, B, and C are all invalid IOS commands.
A48:	Answer: B. The correct syntax is dialer idle-timeout 120. A, C, and D are all invalid IOS commands.
A49:	Answer: B. The value can range from 1 to 255, so 25 is roughly 10%. A is incorrect; 25 is around 10% of the maximum of 255. C is incorrect; the value can range up to 255, not 100. D is incorrect; the value can range up to 255, not 25.
A50:	Answers: A, B, and E. ISDN can be used to transfer not only data, but also voice and video. This makes it an excellent choice for a backup WAN connection. C is incorrect, as signaling occurs only on the delta (D) channel, not the bearer channel (B). D is incorrect, as acknowledgments are a function of Transmission Control Protocol (TCP). Although some of the data being sent may contain acknowledgments, it is not a specific item carried by the B channels.