Tài liệu Cisco® Voice Over IP Exam (CVOICE®) pptx

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CISCO:

Cisco® Voice Over IP Exam (CVOICE®)


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Version 6.0

Jun. 17th, 2003

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Note:
Section A contains 90 questions Section B contains 55 questions. The total number of questions is 145.

Section A
Q.1 A customer in Great Britain needs to install a Cisco router to support IP Telephony services with

direct-connected analog phones. What FXS port parameter do you need to change to emulate the local
PSTN provider?
A. Signal
B. Cptone
C. Busyout
D. Description
Answer: B
Q.2 Your customer is a computer components warehouse. To keep costs low, all inside sales associates are
located at corporate headquarters in another state.
Your customer is interested in providing a direct analog telephone connection to the inside sales teams
from the pick-up counters at their warehouses. This connection will not require the customer to dial any
digits. One of the warehouses is having a problem with their sales phone.
Given the following output:
altwhse#show voice port 1/0:1
Foreign Exchange Office
Type of VoicePort is E&M
Operation State is DORMANT
Administrative State is UP
The Last Interface Down Failure Cause is Administrative Shutdown
Description is not set
Noise Regeneration is enabled
Non Linear Processing is enabled
Music On Hold Threshold is Set to -38 dBm
In Gain is Set to 0 dB
Out Attenuation is Set to 0 dB
Echo Cancellation is enabled
Echo Cancel Coverage is set to 8 ms

Connection Mode is plar
Connection Number is 2000

Initial Time Out is set to 10 s
Interdigit Time Out is set to 10 s
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Call-Disconnect Time Out is set to 60 s
Ringing Time Out is set to 180 s
Region Tone is set for US

What is causing the calls to fail?
A. VoicePort type is incorrect.
B. Echo cancellation is enabled.
C. Connection Number is not required.
D. Interdigit Time Out is set to 10 seconds.
Answer: A

Q.3
Which three types of trunks does Cisco support with the connection trunk command?
(Choose three)

A. FXS to FXS trunks
B. FXS to FXO trunks
C. FXO to FXO trunks
D. E&M to FXS trunks
E. E&M to FXO trunks
F. E&M to E&M trunks
Answer: A, B, F
Q.4 If no incoming dial peer matches a router or gateway, the incoming call leg _____.
A. Takes an alternate path.

B. Matches the default dial peer.
C. Sends a busy to the originator.
D. Is denied and the call does not complete.
Answer: B
Q.5 The following configuration is used at Site A:
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dial-peer voice 20 pots
destination-pattern 20
port 1.0:1

dial-peer voice 41 voip
destination-pattern 41
session target ipv4:10.2.0.20

The following configuration is used at site B:
dial-peer voice 40 pots
destination-pattern 41
port 1.0:1

dial-peer voice 20 voip
destination-pattern 20
session target ipv4:10.4.1.41

To configure a permanent connection between the PBXs, what must be added to the voice port
configuration at site A?
A. connection trunk 20
B. connection trunk 41

C. connection tie-line 20
D. connection tie-line 41
Answer: B Explanation: You must specify the same number in the connection trunk voice port command as in
the appropriate dial peer destination-pattern command in order to create a permanent trunk.
Q.6 A telephony service provider sells managed IP Phone service to businesses in multi-tenant units. The
provider has POPs in many cities, so all of their dial peer patterns are based on 10 digit numbers. Users
dial 9 for local calls, followed by the 7 digital local number.
In a Chicago POP, the following dial peer has been configured:
dial-peer voice 312 pots
destination-pattern 312
port 1/0:24

A user dials a local number, 9-555-0597.
What command must be configured in the gateway to allow the call to complete?
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A. prefix 312
B. forward-digits 7
C. rule 1 9 312
D. num-exp 9 312

Answer: D
Q.7 Which configuration defines a destination pattern for all of the 1000 and 2000 range of extensions
starting with the numbers 555?
A. 5551…
B. 5552…
C. 555[1-2]…

D. 555[1000-2000]…
Answer: C
Q.8 What does RTCP provide?
A. Independent services irrespective of RTP.
B. Compression techniques to save bandwidth.
C. In-band control information for an RTP flow.
D. Out-of-band control information for an RTP flow.
Answer: C
Q.9 What is the disadvantage of using VoIP rather than VoFR or VoATM?
A. Data can arrive out of sequence.
B. Networks are complicated to design.
C. Data units can arrive out of sequence.
D. Network failures are not automatically found.
Answer: C
Q.10 What can you use to verify real-time call control processing in a VoIP network?
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A. debug voip rtcp
B. debug call control
C. debug voip ccapi inout
D. debug voice call control
Answer: C
Q.11 A voice gateway is a box that ______.
A. Connects two dissimilar networks.
B. Transports voice and restricts data.
C. Can support only a distributed call processing model.
D. Cannot be connected to the traditional PSTN network.
Answer: B

Q.12 You have a customer that operates a group of factories. Each factory has an analog phone at each
location. These phones are connected to an FXS port on the on-site router. The press operators are unable
to make any phone class from these analog phones.
Use the following output to resolve the problem:
2611#s voice port 1/0/0
Foreign Exchange Station 1/0/0 Slot is 1, Sub-unit is 0,
Port is 0
Type of VoicePort is FXS
Operation State is DORMANT
Administrative State is UP
No Interface Down Failure
Description is not set
Noise Regeneration is enabled
Non Linear Processing is enabled
Non Linear Mute is disabled
Non Linear Threshold is -21 dB
Music On Hold Threshold is Set to 38 dBm
In Gain is Set to 0 dB
Out Attention is Set to 3 dB
Echo Cancellation is enabled
Echo Cancellation NLP mute is disabled

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Echo Cancellation NLP threshold is -21 dB Echo Cancel Coverage is set to default
Playout-delay Mode is set to default Playout-delay Nominal is set to 60 ms Playout-
delay Maximal is set to 200 ms Playout-delay Minimum mode is set to default, value 40
ms Playout-delay Fax is set to 300 ms Connection Mode is normal Connection Number is

not set Initial Time Out is set to 10 s Interdigit Time Out is set to 10 s Call
Disconnect Time Out is set to 60 s Ringing Time Out is set to 180 Wait Release Time
Out is set to 30 s Companding Type is u-law Region Tone is set for US
Analog Info Follows:
Currently processing none
Maintenance Mode Set to None (not in mtc mode)
Number of signaling protocol errors are 0
Impedance is set to 600r Ohm
Station name None, Station number None

Voice card specific Info Follows:
Signal Type is groundStart
Ring Frequency is 25 Hz
Hook Status is On Hook
Ring Active Status is inactive
Ring Ground Status is inactive
Tip Ground Status is inactive
Digit Duration Status is inactive
Digit Duration Timing is set to 100 ms
InterDigit Duration Timing is set to 100 ms
No disconnect acknowledge
Ring Cadence is defined by CPTone Selection
Ring Cadance are [20 40] * 100 msec

2611#
What is the problem?
A. Incorrect cptone
B. Incorrect dial-type
C. Incorrect signal type
D. Incorrect disconnect-ack

Answer: C Q.13 A company has been using the following dial peer codec command:
Codec g729r8
Over the weekend they reconfigured their dial peers with the following command:
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Codec g729ar8 bytes 10
How does this affect their voice network bandwidth and delay characteristics?
A. There is no change.
B. Per call delays have increased.
C. Per call bandwidth consumption has increased.
D. Both bandwidth and delay have increased on a per call basis.
Answer: D
Q.14 Which two features render VAD ineffective? (Choose two)
A. Fax
B. CNG
C. Call waiting
D. Music on hold
Answer: A, D
Q.15 A user is trying to call another user over a VoIP network and gets a busy tone instead of a dial tone.
What command should you use to troubleshoot the problem?
A. show voice dsp
B. show voice connection
C. show voice port summary
D. show dial-peer voice summary
Answer: A
Q.16 What does compressed RTP significantly reduce?
A. Packet delay
B. Total bandwidth

C. Frame Relay overhead
D. Total number of packets
Answer: B
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Q.17 While installing a voice gateway outside the United States, what two requirements need to be verified?
(Choose two)
A. PSTN standards in that country.
B. Encryption capabilities legalities.
C. The service provider installing the gateway.
D. Supplementary service including fax and modem.
Answer: A, B
Q.18 An MGCP endpoint is identified by a two part identifier that consists of the ______.
A. Telephone number and local name of the user.
B. Telephone number and remote name of the user.
C. Domain name of the user and the IP address of the gateway.
D. Local name of the user and the domain name of the gateway.
Answer: D
Q.19 A customer needs to connect a Cisco voice gateway to a PBX or the PSTN via ISDN (PRI, QSIG, BRI).
What are two attributes of the PBX/PSTN switch that must be known to understand which features to
configure on the voice gateway to connect successfully to it? (Choose two)
A. Whether Q.921 or Q.931 is supported by the PBX/PSTN switch.
B. Whether Symmetric mode is supported by the PBX/PSTN switch.
C. Which PRI/BRI switch-type is supported by the PBX/PSTN switch.
D. Whether network or user side is supported by the PBX/PSTN switch.
E. Whether wink, delay dial, or immediate dial is supported by the PBX/PSTN switch.
Answer: C, D

Q.20 Which protocol negotiates codec type for H.323 sessions?
A. H.225
B. H.245
C. Q.931
D. H.320
Answer: B
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Q.21 Which request method initiates a SIP call setup?
A. ACK
B. INVITE
C. OPTIONS
D. REGISTER
Answer: B
Q.22 Which show command displays the registration of the gateway with the call agent?
A. show mgcp
B. show gateway mgcp
C. show endpoint mgcp
D. show call active voice
Answer: A
Q.23 When gatekeepers communicate with each other, what do they use?
A. RTP
B. RAS channel
C. call signaling channel
D. H.245 control channel
Answer: B
Q.24 To function as a translating gateway, the gateway must ______.

A. Have the capacity to translate the audio.
B. Recognize the call control procedures of both connecting endpoints.
C. Establish separate RTP sessions with the originating and terminating endpoints.
D. Recognize the call control procedures or at least one of the connecting endpoints.
Answer: B

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Q.25
Your customer is having problems completing calls through the MGCP network.
Which command displays a count of the successful and unsuccessful commands?

A. show mgcp
B. show mgcp statistics
C. show call active voice
D. show call history voice
Answer: B
Q.26 Which two call control models are based on decentralized call control? (Choose two)
A. SIP
B. CAS
C. H.323
D. MGCP
Answer: A, C
Q.27 Which four functions are supported by an H.323 gatekeeper? (Choose four)
A. Providing services to registered endpoints.
B. Converting an alias address to an IP address.
C. Translation between audio, video, and data formats.

D. Responding to bandwidth requests and modifications.
E. Conversion between call setup signals and procedures.
F. Conversion between communication control signals and procedures.
G. Limiting access to network resources based on call bandwidth restrictions.
Answer: A, B, D, G
Q.28 Which command is used to specify the IP address of a SIP proxy server?
A. sip-ua
sip-server ipv4:1.2.3.4

B. sip-ua
sip-server target:1.2.3.4
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C. dial-peer voice 1 voip
session target sip:1.2.3.4

D. dial-peer voice 1 voip
session target sip-server:1.2.3.4

Answer: A
Q.29 SIP is similar to H.225 and SDP is similar to ____.
A. RAS
B. RTP
C. H.245
D. H.323
Answer: C

Q.30 Impedance is set on what type of port?
A. T1
B. FXS
C. FXO
D. E&M
Answer: C
Q.31 You have a customer that is deploying an IP telephony solution using MGCP. They understand that
the call agent expects the gateway to use UDP port 2427. The customer would like to use another port
because of a conflict with another application on their network.
If they want to use port 5000, which command allows the customer to change the UDP port their call
agents and gateway communicate on?
A. Router (config)# mgcp UDP 5000
B. Router (config)# mgcp call-agent 5000 Router (config)# mgcp UDP 5000
C. Router (config-dial-peer)#applicatopm MGCPAPP 5000
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D. Router (config)# mgcp default-package gm-package 5000

Answer: B
Q.32 The SIP protocol is based upon which other protocol model?
A. HTML
B. H.323
C. MGCP
D. HTPP/WWW
Answer: D
Q.33 What are two methods that an endpoint can use to determine the address of the gatekeeper? (Choose
two)

A. The endpoint issues a GCP.
B. The endpoint issues a GRQ.
C. The endpoint queries the registrar server.
D. The endpoint is preconfigured to recognize the domain name or IP address of its gatekeeper.
Answer: B, D
Q.34 Exhibit:

In the network shown in the exhibit, if the show gatekeeper calls command shows a total of five active
calls on the gatekeeper, how many call legs would the show call active voice command display on
Gateway A?
A. 1
B. 2
C. 5
D. 6
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E. 10
Answer: E
Q.35 Which two use UDP as their transport mechanism? (Choose two)
A. RTP
B. RAS control function
C. call signalling function
D. H.245 control function
Answer: A, B
Q.36 How is a call defined in the context of MGCP?
A. The path between two telephones.
B. The RTP sessions between the endpoints.

C. A connection between an endpoint and the call agent.
D. Two or more endpoints sharing the same Call ID and the same media stream.
Answer: D
Q.37 Which two are CS-ACELP coding schemes? (Choose two)
A. G.711
B. G.728
C. G.729
D. G-729A
Answer: C, D
Q.38 In ISDN, Q.921 signalling equates to which layer of the OSI model?
A. Session
B. Network
C. Transport
D. Data-Link
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Answer: D
Q.39 Which protocol is designated to allow functionality between two PBX systems from different
manufactures across an ISDN network?
A. QSIG
B. Q.921
C. Q.931
D. T-CCS
Answer: A
Q.40 Which application conveys fax using T.37 fax relay?
A. IVR
B. TCL

C. TIFF
D. SMTP
Answer: D
Q.41 Packet switching is an example of what type of multiplexing?
A. Statistical
B. Time division
C. Phase division
D. Frequency division
Answer: A
Q.42 Which three signal types are used by E&M? (Choose three)
A. loop start
B. wink start
C. delay start
D. immediate start
Answer: B, C, D
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Q.43 Which application enables stock brokerage firms to communicate to multiple remote offices
simultaneously?
A. IP Phone
B. IP Centrex
C. Toll Bypass
D. Multi-tenant
E. Hoot and Holler
Answer: E
Q.44 Which four are attributes of a scalable dialing plan? (Choose four)
A. Logic distribution

B. Hierarchical design
C. Simplicity in provisioning
D. Reduction in pre-dial delay
E. reduction in post-dial delay
Answer: A, B, C, E
Q.45 If no incoming dial peer matches a router or gateway, the incoming call leg _____.
E. Takes an alternate path.
F. Matches the default dial peer.
G. Sends a busy to the originator.
H. Is denied and the call does not complete.
Answer: B
Q.46 In switchwide queuing, what is the recommended configuration for the transmit interface?
A. CoS
B. PFC
C. FIFO
D. 2Q1T
Answer: D

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Q.47
Which three QoS measures, when prompted implemented, affect the outbound queue?
(Choose three)

A. LLQ
B. RSQ
C. WFQ

D. FIFO
E. FRF.12
F. CBWFQ
Answer: A, C, F
Q.48 Traffic engineering for voice is based on a target ______.
A. Peak of service.
B. Class of service.
C. Grade of service.
D. Quality of service.
Answer: C
Q.49 What are modes of the playout delay buffer?
A. Nominal and full.
B. Dynamic and static.
C. Smooth and serrated.
D. Minimum and maximum.
Answer: B
Q.50 In a branch office, one VoIP dial-peer has been configured to point to the company headquarters over
a low speed serial link. Which command would limit the maximum number of concurrent calls to 2?
A. interface serial 3/2
ip rsvp bandwidth 2

B. dial-peer voice 1000 voip
max-conn 2
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C. dial-peer voice 1000 voip

max-concurrent 2

D. dial-peer voice 1000 voip
ip rsvp neighbor 2

Answer: B
Q.51 Which three are categories for QoS in a campus network? (Choose three)
A. Queue scheduling
B. Pruning of queues
C. Separation of queues
D. Marking control and management traffic
Answer: A, C, D
Q.52 When does glare occur?
A. When echo cancellers fail to synchronize.
B. When two phones go off-hook at the same time.
C. When two optical wavelengths collide in the same fiber.
D. When both ends of a telephone line or trunk are seized by different users.
Answer: D
Q.53 If a network link is oversubscribed, ______.
A. The link goes down.
B. All voice calls suffer.
C. Voice packets are fragmented.
D. Data packets are given priority.
E. Excess voice calls are dropped.
Answer: B
Q.54 CAC is a concept that applies to ____ only.
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A. Latency
B. Data traffic
C. Voice traffic
D. TCP networks
Answer: C
Q.55 Which FRF.x standard defines fragmentation for VoIP over Frame Relay?
A. FRF.5
B. FRF.6
C. FRF.11
D. FRF.12
Answer: D
Q.56 Which command shows the status of LLQ on the interface serial 3/2?
A. show class 11q
B. show interface serial 3/2
C. show queue interface serial 3/2
D. show interface serial 3/2 class 11q
E. show policy-map interface serial 3/2
Answer: E
Q.57 Why is Frame Relay traffic shaping an important tool for ensuring the delivery of traffic?
A. It ensures that voice packets are not trapped behind large data packets.
B. It ensures that the priority of the voice packet is higher than the data packets.
C. It ensures that the RTP headed is reduced in size to reduce the overall size of the voice packet.
D. It ensures that excess traffic above the CIR on the link is not dropped, but is buffered and sent when there
is capacity on the link.
Answer: D

Q.58 A branch office is using a 128 kbps Frame Relay link to connect to the company headquarters. Which
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two QoS mechanisms should be implemented on the Frame Relay interface to ensure good voice quality?
(Choose two)
A. CIR
B. LLQ
C. WFQ
D. WRED
E. Fragmentation
Answer: B, E
Q.59 What component can compensate for jitter?
A. FIFO queuing
B. Ethernet hubs
C. DSP algorithms
D. Playout delay buffer
Answer: D
Q.60 What delay range is considered acceptable according to the G.114 standard?
A. 0 - 150 ms
B. 0 - 250 ms
C. 0 - 400 ms
D. 0 - 500 ms
Answer: A
Q.61 Which two factors affect audio quality? (Choose two)
A. Echo
B. Infidelity
C. Delay variation
D. Transmission medium
Answer: A, C
Q.62 If the playout delay buffer size is configured too large, the overall ______ on the connection may rise

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to unacceptable levels.
A. Echo
B. Delay
C. Stress
D. Volume
Answer: B
Q.63 Which four does the TCP’s reliable deliver service provide? (Choose four)
A. Flow control
B. Sequenced delivery
C. Unregulated send rate
D. Connectionless service
E. Automatic error recovery
F. Transmission window management
Answer: A, B, E, F
Q.64 You have a customer that is interested in deploying an IP telephony solution in their organization.
The network today is a traditional LAN/WAN The WAN is based on Frame Relay.
The customer has read about the issues of converging both their data and voice traffic onto a single
network. They are especially concerned about the quality of their calls that need to cross the WAN.
What are the recommended five major components of QoS for VoIP over Frame Relay? (Choose five)
A. Fragmentation
B. Traffic shaping
C. Priority queuing
D. Low Latency Queuing
E. Call Admission Control
F. Link efficiency with cRTP

G. Weighted Random Early Detection
H. Class Based Weighted Fair Queuing
Answer: A, B, C, D, F
Q.65 Your customer has deployed VoIP over their WAN. Early in the workday, the quality of calls between
headquarters and the three branch offices is very good, but as the day goes on and more calls are placed to
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the branch offices, the quality degrades. Using RSVP, the WAN bandwidth to the branch offices allows 4
calls to branch A, 6 calls to branch B, and 8 calls to branch C. What command allows you to verify the
configuration of Call Admission Control on the headquarters router?
A. show call cac conf
B. show call rsvp-sync conf
C. show call rsvp-sync stats
D. show call rsvp-sync events
Answer: B
Q.66 What is the worst-case compression delay for CD-ACELP?
A. 2.5 ms
B. 5 ms
C. 10 ms
D. 20 ms
Answer: D
Q.67 A call leg is considered what type of connection?
A. Digital
B. Logical
C. Physical
D. Hardwired
Answer: B

Q.68 When the requirement is for users at site A to be able to call users at site B and vice versa, how many
dial peers must be configured for end-to-end calls in both directions?
A. 0
B. 2
C. 3
D. 4
Answer: D
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Q.69 Which three issues adversely affect voice quality on an IP network? (Choose three)
A. Jitter
B. Delay
C. Packet loss
D. Prioritization
E. Acknowledgment
F. Delivery guarantee
Answer: A, B, C
Q.70 When implementing IPSEC VPNs in the converged network, what is the biggest issue affecting voice
transport?
A. Hop count.
B. Using G.729 as the codec.
C. Throughput considerations.
D. Ensuring only software encryption is running.
Answer: C
Q.71
When employing an IPSEC VPN for transport of voice, what factors must be incorporated into the overall
design?

A. Port numbers and added delay.
B. Added delay and added overhead.
C. Port numbers and added overhead.
D. Added overhead and longer dial plan.
Answer: C
Q.72 What do VoIP implementations use?
A. RTP only
B. UDP only
C. UDP inside RTP to carry the payload across the network.
D. RTP inside UDP to carry the payload across the network.
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Answer: D
Q.73 The PBX determines the destination of a call based upon ______.
A. and ISDN ANI packet
B. a blocked/permitted call list
C. an analysis of the dialled digits
D. historic requests from the specific phone extension
Answer: C
Q.74 What carries VoIP voice packets?
A. ICMP/IP
B. RTP/TCP
C. RTP/UDP
D. STP/UDP
E. RTP/RCMP
Answer: C
Q.75 The Real-Time Protocol (RTP) uses which lower layer protocol?

A. TCP
B. UDP
C. WDP
D. HTTP
E. RTCP
Answer: B
Q.76 What describes the formula for encoding PCM?
A. 2 states per bit x 8000 Hz frequency coded into 4 bits = 64 kbps
B. 8000 Hz frequency encoded in 4 bits, each expanded by two = 64 kbps
C. 3400 Hz voice frequency represented in 8 bits x 2 states per bit = 56 bkps
D. 4000 Hz frequency sampled at two times the frequency and each sample is represented in 8 bits = 64 kbps