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Cisco ICOMM 640-461 Flashcards

CCNA Voice 640-461 Exam Preparation

1
Q

List the two wires and polarity that make up an analog circuit pair.

A

ground (aka tip) is the positive side and battery (aka ring) is the negative side

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2
Q

Describe loop start signaling.

A

When a phone goes off hook and the tip and ring wires connect causing a 48v DC signal from the phone company CO.

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3
Q

What problem with loop start signaling prompted the creation of ground start signaling.

A

Glare (when an outgoing call and incoming call occur at the same time connecting the two sides)

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4
Q

What digital voice technology allows multiple concurrent calls over a single 4-wire cable?

A

Time-Division Multiplexing

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5
Q

What type of circuit uses a digital voice connection?

A

T1

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6
Q

What two styles of signaling were created for digital voice?

A

Channel Associated Signaling and Common Channel Signaling

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7
Q

Describe CAS and CCS signaling.

A

CAS signaling info is transmitted using the same bandwidth as the voice whereas CCS uses a separate dedicated signaling channel.

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8
Q

What is another name for CAS?

A

RBS (Robbed Bit Signaling)

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9
Q

Which frame and bit is stolen for signaling using CAS?

A

The 8th bit of every 6th frame for each DS0 channel.

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10
Q

CCS is also referred to as…

A

Out-of-band signaling.

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11
Q

How many voice channels are available with CAS and CCS respectively?

A

24 and 23

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12
Q

Which CCS time slots are used for T1 and E1 signaling channels respectively?

A

24th and 17th

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13
Q

What out-of-band PSTN signaling method is used by all COs worldwide to communicate?

A

SS7

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14
Q

What is the max length of an E.164 number?

A

15 digits

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15
Q

Want are the components of the E.164 numbering plan?

A

Country code, national destination code, and subscriber number

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16
Q

What is the process of converting analog to digital voice?

A

Quantization

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17
Q

What is the relationship between G.711 μ-law and G.711 a-law?

A

They are exactly opposite. A 0 in the G.711 μ-law codec will be a 1 in a-law.

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18
Q

What is the measurement used to rate the quality of the various voice codecs?

A

MOS (Mean Opinion Score)

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19
Q

What is a DSP?

A

Digital Signal Processors are a chip that offloads the sampling, encoding, and compression from the router processor.

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20
Q

Give an examples of medium and high complexity codecs.

A

G.711 (a-law and μ-law) is medium and G.729 is high.

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21
Q

How many RTP streams are used for a call?

A

Two - one for each direction.

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22
Q

What is the function of Real-Time Transport Control Protocol?

A

RTCP reports statistics between two devices such as packet count, packet delay, packet loss, jitter.

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23
Q

Is RTP or RTCP more critical to a voice call?

A

RTP since it contains the actual audio. RTCP only reports statistics.

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24
Q

What is the range of UDP ports used by RTP an RTCP?

A

16,384 to 32,767. RTP uses even port numbers and RTCP uses odd.

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25
Q

What will be the UDP port number of the RTCP session if RTP is using port 17,654?

A

RTCP will use 17,655

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26
Q

What signalling protocol is used between CME and CUE?

A

SIP

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27
Q

What is the max number of IP phones supported by a CUCM cluster?

A

30,000 IP phones (SCCP or SIP in unsecure mode) or 27,000 IP phones (SCCP or SIP in secure mode).

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28
Q

What type of signaling is used when an IP phone registers to a server that is part of a cluster?

A

The server will inform other servers in the cluster using Intra-Cluster Communication Signaling (ICCS).

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29
Q

Which transport protocol and ports are used by Intracluster Communication Signaling (ICCS)?

A

TCP ports 8002 - 8004.

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30
Q

What CUCM server in a cluster holds the master copy of the database?

A

The Publisher.

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31
Q

What type of servers and how many of each are supported within a single cluster.

A

1 Publisher and up to 8 Subscribers.

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32
Q

What is the max number of mailboxes and ports on Unity Connection?

A

20,000 mailboxes and 250 ports.

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33
Q

What are the two primary functions of the CUCM Publisher?

A

It maintains the database and serves TFTP requests. The Publisher can handle call processing, but the Subscribers do most of the heavy lifting in deployments of 500 phones or more.

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34
Q

Is the MWI extension on the CUCM or Unity Connection server?

A

MWI extension is on the CUCM server. Unity Connection calls the extension to let the user know they have a voicemail.

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35
Q

True or False: The CUCM publisher is always the primary server?

A

False. The primary server is the server a particular phone is registered to in a cluster. There are multiple primary servers within a cluster.

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36
Q

How does a Cisco IP phone learn the voice VLAN from a switch.

A

CDP

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37
Q

What DHCP option indicates the TFTP server address for IP phones?

A

Option 150

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38
Q

Describe the 5 steps in the Cisco IP phone boot process.

A
  1. The PoE switch detects an unpowered device and supplies power to the phone.
  2. The switch sends the voice VLAN info to the phone using CDP.
  3. The phone sends a DHCP request and the server replies including option 150 for TFTP.
  4. The phone downloads firmware and config file.
  5. The phone contacts the call processing server.
39
Q

What telephony service subcommand configures an external TFTP server for phone firmware and config files?

A

cnf-file location tftp://

40
Q

List the three telephony-service subcommands necessary to enable the phone system.

A

ip source address
max-dn
max-ephones

41
Q

What is the difference between a single-line and dual-line ephone-dn?

A

Single-line will only support 1 call at a time. Another call will receive the busy signal. Dual-line can accept 2 calls.

42
Q

What show command will display analog ports on the router?

A

show voice port summary

43
Q

What is the default FXS signaling type?

A

Loop start

44
Q

What are the two FXS signaling types and when are they typically used?

A

Ground start when connecting to PBX equipment and loop start when connecting to analog devices such as phones and fax machines.

45
Q

List the commands used to configure caller ID information on an FXS port.

A

voice-port (0/0/0)
station-id name (name)
station-id number (number)

46
Q

What is the default number of rings on a FXO port before the router answers and what is the port subcommand to change this?

A

1 ring, ring number (number)

47
Q

What controller subcommand enables T1 CAS signaling?

A

ds0-group (number) timeslots (1-24) type (fxo-loop-start)

48
Q

What controller subcommand enables T1 CCS signaling?

A

pri-group timeslots (1-24)

49
Q

What show command displays T1 interfaces on the router?

A

show controllers t1

50
Q

What is the default service provider framing and linecoding in the US?

A

Extended Super Frame (ESF) framing and B8ZS linecoding

51
Q

Which T1 controller subcommand instructs the router to receive its interface clocking from the service provider?

A

clock source line

52
Q

Which T1 controller subcommand allows the router to provide clocking information to a PBX system?

A

clock source internal

53
Q

What is the range of values for ds0-group group numbers?

A

0 to 23

54
Q

What is the channel and timeslot for all T1 ISDN PRI connections

A

Channel 23 (timeslot 24) is the voice bearer channel for all PRI connections.

55
Q

List the commands to configure a T1 CCS PSTN interface.

A 
isdn switch-type (primary-5ess)
controller t1 (1/0)
pri-group timeslots (1-24)
56
Q

List the dial-peer configuration commands to assign extension 1101 to FXS port 0/0/0

A

dial-peer voice (1101) pots
destination-pattern 1101
port 0/0/0

57
Q

What show command lists dial-peers by tag and port?

A

show dial-peer voice summary

58
Q

List the dial-peer configuration commands for T1 PRI to all 2xxx extensions on port 1/0.

A

dial-peer voice 2000 pots
destination-pattern 2…
no digit-strip
port 1/0:23

59
Q

Describe automatic digit stripping as it relates to POTS dial-peers.

A

POTS dial-peers automatically strip explicit digits unless “no digit-strip” is configured. For example, the “2” would be stripped from “destination-pattern 2…”.

60
Q

List the commands to configure a VoIP dial-peer for 110x extensions to 10.1.1.1 using g711ulaw.

A

dial-peer voice 1100 voip
destination-pattern 110.
session target ipv4:10.1.1.1
codec g711ulaw

61
Q

What is the default codec for VoIP dial-peers?

A

G.729

62
Q

Interdigit timeout is also referred to as…

A

T302 timer

63
Q

Which digits will be sent if a POTS dial peer is configured with a destination-pattern 9[469]11 and forward-digits 3?

A

The 9 will be stripped and 411, 611, or 911 will be forwarded.

64
Q

Assume a POTS dial peer with destination-pattern 9011T and prefix 011. What digits will be sent when dialing 9011234?

A
  1. Otherwise, only 234 would be sent without the prefix command because of automatic digit stripping.
65
Q

Describe Private Line Automatic Ringdown.

A

A phone automatically dials a predefined number as soon as it goes off-hook.

66
Q

Extension 1101 is mapped to FXS port 0/0/0. List the configuration commands to setup PLAR to 1102.

A

voice-port 0/0/0

connection plar 1102

67
Q

List the commands to configure PLAR on FXO port 0/1/0 to forward calls to extension 1101.

A

voice-port 0/1/0

connection plar 1101

68
Q

What show command is used to test dial strings and display dial-peer matches in order?

A

show dialplan number (number)

69
Q

What dial-peer subcommands can be used to match inbound calls?

A 
incoming called-number (DNIS)
answer-address (ANI)
destination-pattern (ANI)
port (FXS/FXO)
dial-peer 0
70
Q

Describe the process of creating an automatic failover.

A

Create 2 dial peers with the same destination pattern using preference 0 and 1.

71
Q

What global configuration command can be used to transform one number to another, such as 0 for the operator to the recetptionist at extension 5000?

A

num-exp 0 5000

72
Q

What command is used to test translation rules?

A

test voice translation-rule (rule number) (string)

73
Q

What show command is used to test dial strings and display dial-peer matches in order?

A

show dialplan number (number)

74
Q

What dial-peer subcommands can be used to match inbound calls?

A 
incoming called-number (DNIS)
answer-address (ANI)
destination-pattern (ANI)
port (FXS/FXO)
dial-peer 0
75
Q

Describe the process of creating an automatic failover.

A

Create 2 dial peers with the same destination pattern using preference 0 and 1.

76
Q

What global configuration command can be used to transform one number to another, such as 0 for the operator to the recetptionist at extension 5000?

A

num-exp 0 5000

77
Q

What command is used to test translation rules?

A

test voice translation-rule (rule number) (string)

78
Q

What happens if no incoming or outgoing COR list is assigned to the ephone-dn or dial-peer?

A

The call is always routed.

79
Q

True or False: COR always requires an inbound COR list meeting an outbound COR list.

A

True

80
Q

What is jitter?

A

The variation in delay between packets.

81
Q

What are the bandwidth (delay, jitter, packet loss) requirements for one-way voice?

A

delay 150 ms or less, jitter 30 ms or less, 1% or less

82
Q

What QoS mechanism guarantees bandwidth using the Resource Reservation Protocol (RSVP)?

A

Integrated Services (IntServ)

83
Q

What are the main differences between policing and shaping traffic?

A

Policing is used to limit bandwidth for certain network traffic (bandwidth hogs) and it typically drops excess traffic. Shaping is designed for networks where actual speed allowed is slower than interface speed and it typically queues excess traffic.

84
Q

List three link efficiency mechanisms and when to use?

A

Payload compressioin, header compression, and Link Fragmentation and Interleaving (LFI). Use only on links slower than T1 speed.

85
Q

Desribe Weighted Fair Queuing.

A

Bandwidth is balanced evenly among all senders.

86
Q

Describe Class-Based Weighted Fair Queuing.

A

Defined traffic classes are guaranteed bandwidth (a specific percent or set amount), and all other traffic is queued using WFQ.

87
Q

Describe Low Latency Queuing (AKA PQ-CBWFQ).

A

LLQ is the same as CBWFQ except it adds a priority queue component.

88
Q

What is the preferred queuing algorithm for voice?

A

LLQ

89
Q

Which two QoS mechanisms can be used on both inbound and outbound interfaces?

A

Marking and policing.

90
Q

How does Auto-QoS detect Cisco IP phones?

A

CDP

91
Q

Which queuing method is used by Cisco AutoQoS?

A

Low Latency Queuing

92
Q

What switch interface subcommand enables AutoQoS for a Cisco IP phone?

A

auto qos voip cisco-phone

93
Q

What switch interface subcommand enables AutoQoS for a connection to a Cisco router?

A

auto qos voip trust

94
Q

What interface subcomman enables AutoQos on router Ethernet and serial interfaces?

A

auto qos voip trust

Cisco (7 decks)

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