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Pass4sure Cisco IP Communications Exam 642-642 v2.73

IP Communications Quality of Service (QoS) : 642-642 Exam

Exam Number/Code: 642-642
Exam Name: IP Communications Quality of Service (QoS)
VUE Code: 642-642
Questions Type: Single choice,
Question Numbers of Real-exam: 45-55 questions

Exam : Cisco 642­642

Title :

Cisco. Quality of Service (QoS)

Update : Demo

1.What is the purpose of the qos pre­classify command?
A. to enable the IOS to copy the ToS field from the original IP header to the outer tunnel IP header
B. to enable the IOS to copy the ToS field from the outer tunnel IP header back into the original IP header
C. to enable the IOS to classify the packet based on the original IP header instead of the tunnel IP header
D. to enable the IOS to classify the packet based on the outer tunnel IP header instead of the original IP
header
E. to enable class­based marking on tunnel interface
F. to enable class­based marking on IPSec crypto maps
Answer: C

2.What are two benefits of WFQ? (Choose two.)
A. WFQ is very easy to configure, and no manual traffic classification is necessary. B. WFQ can provide fixed­bandwidth and fixed­delay guarantees.
C. WFQ can provide fixed­bandwidth guarantees. D. WFQ can provide fixed­delay guarantees.
E. WFQ prevents the large­volume flows with large packet size from starving out the low­volume flows with small packet size.
F. Based on DSCP, WFQ allows weighted, random dropping of packets when the WFQ system is full. Answer: AE

3.Based on the configuration, which two of the following statements are true? (Choose two.)

A. This configuration will use a single token bucket.
B. This configuration will drop all exceeding traffic.
C. This is a dual­rate, class­based policing example. D. This is a percentage­based policing example.
E. This is a multi­action, class­based policing example. Answer: CD

4.Based on the configuration, which two statements are true? (Choose two.)

A. The interactive traffic class will have a minimum bandwidth guarantee of 256 kbps.
B. The interactive traffic class will have a maximum bandwidth guarantee of 256 kbps.

C. If the interactive traffic class exceeds an average rate of 256 kbps, the traffic rate will be throttled down
to 128 kbps.
D. This configuration allows class­based traffic shaping to lower the traffic rate in response to the BECN
bit.
E. The interactive traffic class will have a min­rate (min­cir) of 128 kbps. Answer: DE

5.Which technology is required when configuring FRF.12 on a Cisco device? A. FRF11.c
B. FRF.8
C. VoFR
D. MLP with interleaving
E. FRTS F. WRED Answer: E

6.What are three methods of reducing delay for critical applications in a converged network? (Choose three.)
A. Apply payload compression. B. Increase link capacities.
C. Apply header compression. D. Increase LFI fragment size. E. Reduce inter­packet gaps.
F. Increase all queue depths. Answer: ABC

7.At the network layer, IP packets are typically classified based on which three items? (Choose three.)
A. packet length
B. VLAN Identifier
C. flow control bits
D. source and destination IP addresses
E. content of the ToS byte
Answer: ADE

8.What are three reasons link efficiency mechanisms are deployed on WAN links? (Choose three.)
A. decrease delay
B. decrease jitter
C. increase link speed
D. increase throughput
E. decrease propagation delay
Answer: ABD

9.Which mechanism is used for the prioritizing, protection, and isolation of traffic based on marking?
A. classification and marking

B. congestion management
C. congestion avoidance
D. metering E. policing F. shaping Answer: B

10.For which service is assured forwarding PHB used? A. best effort
B. expedited forwarding C. guaranteed bandwidth D. class selector
Answer: C

11.Which three factors will affect processing delay? (Choose three.) A. CPU speed
B. router architecture
C. queuing mechanism
D. type of media
E. IP switching method F. distance of media Answer: ABE

12.which four of the following bit values are used for bits 5­7 of the DSCP field to select AF PHB? (Choose four.)
A. 000
B. 001
C. 010
D. 011
E. 100
F. 101
Answer: BCDE

13.Based on the following 2950 switch configurations, which statement is correct?

A. Queue 1 is setup as the expedite queue.
B. Queue 2 is setup as the expedite queue. C. Queue 3 is setup as the expedite queue. D. Queue 4 is setup as the expedite queue. E. No queue is setup as the expedite queue.
Answer: E

14.When LLQ is being configured, which IOS command is used to limit the traffic rate on the priority queue even when the other class queues are not congested?
A. priority
B. bandwidth C. queue­limit D. police
E. hold­queue
Answer: D

15.Where is the error in the following policy­map configuration?

A. The bandwidth command is not a valid command for the class­default traffic class in this case.
B. The voice traffic class is missing the random­detect command.
C. The mission­critical traffic class bandwidth guarantee should be lower than the voice traffic class priority bandwidth guarantee.
D. The mission­critical traffic class is missing the queue­limit command. E. Fair­queue should be enabled for the mission­critical traffic class. Answer: A

16.QoS policy propagation through BGP (QPPB) supports which two QoS markers? (Choose two.)

A. DSCP
B. IP precedence
C. QoS group
D. COS
E. MPLS EXP Answer: BC

17.Which element is mandatory for QoS policy propagation through BGP operations? A. MPLS
B. NBAR C. CEF
D. QoS pre­classify
E. policy­based routing
F. MQC Answer: C
18.Based on the following policy­map configuration, the bulk traffic class packets are not being ECN
marked, yet there are many random drops in the bulk traffic class. What is the most likely cause of the

problem?

A. The CB­WRED min threshold is set too low.
B. The CB­WRED max threshold is set too high.
C. The CB­WRED mark probability denominator is set too low.
D. The endpoints generating the bulk traffic packets are not ECN capable. E. Some of the routers within the traffic path are not ECN capable.
Answer: D

19.Which two of the following statements about CBWFQ are correct? (Choose two.)
A. The CBWFQ scheduler provides a guaranteed amount of minimum bandwidth to each class.
B. CBWFQ services each class queue using a strict priority scheduler. C. The class­default queue only supports WFQ.

D. Each CBWFQ traffic class is policed using a congestion aware policer.
E. Inside a class queue, processing is always FIFO, except for the class­default queue. Answer: AE

20.Which of the following configurations requires the use of hierarchical policy maps? A. the use of class­based WRED within a CBWFQ class queue
B. the use of a strict priority­class queue within CBWFQ C. the use of CBWFQ inside class­based shaping
D. the use of nested class­maps with class­based marking
E. the use of both the bandwidth and shape statements within a CBWFQ class queue Answer: C

21.The following commands have been configured under the fa0/1 interface on the 2950 switch: Voice
traffic from the IP phone that is directly connected to the fa0/1 interface is experiencing excessive delays.

What could be the cause of this problem?

A. The wrr­queue bandwidth weightings are not correct. B. The default wrr­queue cos­map is being used.
C. The default cos­to­dscp map is being used. D. The default dscp­to­cos map is being used.
E. The trust boundary configuration is not correct. Answer: B

22.Which QoS mechanism adds IP Precedence information for prefixes into the FIB table?
A. QoS pre­classify
B. AutoQoS C. QPPB
D. Class­Based Marking
E. LLQ
F. Class­Based WRED Answer: C

23.Refer to the partial router configuration. Which two of the following statements are true? (Choose two.)

A. The configuration is invalid since it refers to a class map within a different class.
B. The class­map class1 command will set the qos­group value to 4 for all IP packets.
C. Regardless of destination IP address, all traffic sent to Mac address 1.2.3 will be subject to policing
D. Only those packets which satisfy all of the matches in class1 and class2 will be subject to policing.
E. All traffic from a server with the IP address of 147.23.54.21 will be subject to policing.
F. Any IP packet will be subject to policing. Answer: CE

24.In a typical converged campus network, which two of the following are considered QoS best practices?
(Choose two.)
A. Traffic classification and marking is performed as close to the traffic source as possible.
B. Traffic classification and marking is performed at the high speed core layer. C. Ensure voice traffic is serviced by a weighted fair queue.
D. Only a reasonable number of applications should be classified into the mission­critical traffic class.
E. NBAR is used at the high speed core layer to discover and classify network applications.
F. Catalyst switches should use weighted round robin (WRR) queuing giving the voice traffic the highest priority.
Answer: AD

25.Which three characteristics are drawbacks to the use of a best­effort with over­provisioning backbone design? (Choose three.)
A. The design costs more to implement than a DiffServ backbone.
B. Denial of Service attacks on one service can affect all network traffic.
C. The design uses a different over­provisioning ratio for the different traffic classes. D. It requires complex QoS mechanisms at the network edge.
E. It requires complex QoS mechanisms at the network core.
F. Unplanned network failures can cause unexpected congestion in the network. Answer: ABF

26.Which two different traffic types have the most similar sensitivity to latency, jitter, and packet loss?
(Choose two.)
A. SQL transactions
B. voice
C. voice signaling
D. streaming video
E. video conferencing
F. peer­to­peer file sharing
Answer: BE

27.To determine the bandwidth requirement for each VoIP call, not including Layer 2 overhead, how much bandwidth per call should be added to account for the voice signaling traffic?
A. 20 bps B. 40 bps C. 150 bps D. 240 bps E. 480 bps F. 640 bps Answer: C

28.What does the following command accomplish?

A. enables the router to lower the shaping rate when BECN bits are received
B. enables the router to lower the shaping rate when FECN bits are received
C. enables the router to respond to FECN bits by creating test frames in the opposite direction with the
BECN bit set
D. enables the router to respond to BECN bits by creating test frames in the opposite direction with the
FECN bit set
E. enables the router to increase the shaping rate when BECN bits are received
F. enables the router to increase the shaping rate when FECN bits are received
Answer: C

29.What will be the peak shape rate based on the configuration that follows?

A. 16000 bps
B. 32000 bps

C. 48000 bps
D. 64000 bps E. 80000 bps F. 96000 bps Answer: D

30.Which QoS mechanism calculates the mean queue depth to determine its operation?
A. WRED
B. LLQ/CBWFQ C. WFQ
D. class­based shaping E. class­based policing Answer: A

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“IP Communications Quality of Service (QoS)”, also known as 642-642 exam, is a Cisco certification.
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With the complete collection of questions and answers, Pass4sure has assembled to take you through 90 Q&As to your 642-642 Exam preparation. In the 642-642 exam resources, you will cover every field and category in IP Communications helping to ready you for your successful Cisco Certification.
Questions and Answers : 90 Q&As
Updated: April 24th , 2008
Market Price: $125.99
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The QOS exam is one of the qualifying exams for the Cisco Certified Internetwork Professional, Cisco Certified Voice Professional, Cisco IP Telephony Design Specialist, Cisco IP Telephony Express Specialist, Cisco IP Telephony Operations Specialist, and Cisco IP Telephony Support Specialist certifications. The QOS 642-642 exam will test materials covered under the Implementing Cisco Quality of Service QOS v2.1 course. The exam will certify that the successful candidate has knowledge and skills necessary to configure and troubleshoot Cisco IOS routers running Quality of Service protocols in Service Provider and Enterprise environments. The exam covers topics on IP QOS, classification and marking Mechanisms, queuing mechanisms, traffic shaping and policing mechanisms, congestion avoidance mechanisms, link efficiency mechanisms, modular QOS command line interface, and QOS Best Practices.
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