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QUESTION 49
Refer to the exhibit.

A service provider moved from a three-class service provider QoS model to a four-class service provider QoS model. A new class of service called CRITICAL-B was created to support traffic with a DSCP marking of AF31. A customer reports that the traffic in the CRITICAL-B class is having problems. What step should the service provider take to correct this issue?
A. The class map for CRITICAL-B should have a DSCP value of 28.
B. The max-reserved-bandwidth command must be used to allocate more bandwidth than allowed by default.
C. The policy map should be updated to move the BULK class to the bottom of the policy.
D. The CRITICAL-A class should change from match-all to match-any.
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 50
The provider you work for supports a wide range of Cisco router models and Cisco IOS Software releases. You are in the process of moving to a SNMP-based tool to monitor QoS configurations and statistics. What are some of the challenges to this approach?
A. The SNMP MIB provides direct access into the QoS configuration parameters. Poor configuration could lead to changes that are difficult to track.
B. Some models of Cisco routers do not have full support for the class-based QoS MIB, which results in a number of elements that cannot be managed.
C. Older versions of Cisco IOS Software do not maintain index persistency, which results in significant changes in the information that is collected unless properly configured.
D. SNMP should be used in conjunction only with Cisco IP SLA to ensure that the information gathered is reported properly.
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Interface Index Persistence feature introduced in Cisco IOS Release 12.1(5)T. This enhancement allows interfaces to be identified with unique values which will remain constant even when a device is rebooted. These interface identification values are used for network monitoring and management using Simple Network Management Protocol (SNMP)
One of the identifiers most commonly used in SNMP-based network management applications is the interface index (ifIndex) value. IfIndex is a unique identifying number associated with a physical or logical interface; as far as most software is concerned, the ifIndex is the “name” of the interface.
Although there is no requirement in the relevant RFCs that the correspondence between particular ifIndex values and their interfaces be maintained across reboots, applications such as device inventory, billing, and fault detection increasingly depend on the maintenance of this correspondence.
Cisco IOS Release 12.1(5)T adds support for an ifIndex value that can persist across reboots, allowing users to avoid the workarounds previously required for consistent interface identification.
It is currently possible to poll the router at regular intervals to correlate the interfaces to the ifIndex, but it is not practical to poll this interface constantly. If this data is not correlated constantly, however, the data may be made invalid because of a reboot or the insertion of a new card into the router in between polls. Therefore, ifIndex persistence is the only way to guarantee data integrity.
IfIndex persistence means that the mapping between the ifDescr object values and the ifIndex object values (generated from the IF-MIB) will be retained across reboots.
Benefits
Association of Interfaces with Traffic Targets for Network Management
The Interface Index Persistence feature allows for greater accuracy when collecting and processing network management data by uniquely identifying input and output interfaces for traffic flows and SNMP statistics. Relating each interface to a known entity (such as an ISP customer) allows network management data to be more effectively utilized.
Accuracy for Mediation, Fault Detection, and Billing
Network data is increasingly being used worldwide for usage-based billing, network planning, policy enforcement, and trend analysis. The ifIndex information is used to identify input and output interfaces for traffic flows and SNMP statistics. Inability to reliably relate each interface to a known entity, such as a customer, invalidates the data.
Restrictions
The interface-specific ifIndex persistence command ([no] snmp ifindex persistence) cannot be used on subinterfaces. A command applied to an interface is automatically applied to all the subinterfaces associated with that interface.
Testing indicates that approximately 25 bytes of NVRAM storage are used by this feature per interface. There may be some boot delay exhibited on platforms with lower CPU speeds
QUESTION 51
Which statement about when you mix TCP and UDP traffic in the same class and overflow occurs is true?
A. UDP traffic suffers more, because TCP guarantees delivery.
B. TCP traffic is starved, because UDP never slows down when packets get dropped.
C. The overflow is not a problem, because both TCP and UDP packets get randomly dropped and traffic will back out.
D. Mixing TCP and UDP in the same class is not supported.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
QUESTION 52
A provider plans to use IP SLA to help diagnose future performance issues in their PE routers in the network. Which two should be considered by the provider? (Choose two.)
A. IP SLA requires a significant amount of resources to operate properly. Using IP SLA on the PE routers will only aggravate performance-related issues the network already encounters.
B. IP SLA is supported only on Cisco IOS edge routers, because it simulates traffic from the network endpoints.
C. IP SLA should be implemented on dedicated hardware to properly simulate network endpoints
D. IP SLA should use a mix of source and target points.
Correct Answer: CD Section: (none) Explanation
Explanation/Reference:
QUESTION 53
Refer to the exhibit.

A provider uses the recommended mappings for DSCP to MPLS EXP. Several sites connected to the same PE router report that critical data has been experiencing a high number of drops. The
customer marks its CRITICAL data as AF31. What appears to be the problem?
A. The classification for CRITICAL-DATA should contain a match-all, not a match-any.
B. The provider is using the recommended mappings for DSCP to MPLS EXP, so the CLASSMAP for the CRITICAL-DATA should contain EXP value of 4.
C. The recommended mapping for AF31 is to MPLS EXP 5, which is classified in the REALTIME class, not the CRITICAL DATA class.
D. The allocated bandwidth for CRITICAL-DATA should be increased to provide sufficient bandwidth to support the application.
E. If the data receiving drops is high priority, it should be marked with MPLS EXP value 7.
Correct Answer: B Section: (none) Explanation
Explanation/Reference: MPLS Experimental Field
Setting the MPLS experimental (EXP) field value satisfies the requirement of service providers who do not want the value of the IP precedence field modified within IP packets transported through their networks.
By choosing different values for the MPLS EXP field, you can mark packets so that packets have the priority that they require during periods of congestion.
By default, the IP precedence value is copied into the MPLS EXP field during imposition.You can mark the MPLS EXP bits with an MPLS QoS policy.
DSCP CS1 is mapped into EXP 1

QUESTION 54
What are three fundamental QoS mechanisms? (Choose three.)
A. congestion avoidance
B. undersubscription
C. congestion handling D. policing
E. marking
Correct Answer: ADE Section: (none) Explanation
Explanation/Reference:
QUESTION 55
Which three issues are important challenges for monitoring service quality in the SP core network? (Choose three.)
A. Multiple flows compete for a limited amount of bandwidth
B. Packets have to traverse many network devices and links that add up to the overall delay.
C. Traffic flows are continuously high.
D. Packets may have to be dropped when a link is congested
E. Relatively few tools are available for collecting service quality data.
Correct Answer: ABD Section: (none) Explanation
Explanation/Reference:
QUESTION 56
Refer to the exhibit.

Which two statements about the SP-REALTIME traffic class are true? (Choose two.)
A. Traffic is queued using LLQ
B. Traffic is policed to 35 percent of the interface bandwidth.
C. The priority configuration command is missing the maximum guaranteed bandwidth rate.
D. The police configuration command is missing the violate-action option.
E. Traffic conforming to the police rate will be transmitted and all the markings on the packets will be cleared.
Correct Answer: AB Section: (none) Explanation
Explanation/Reference:
QUESTION 57
Refer to the exhibit on a PE router. What could be causing the issue?

Service-policy output: OUTPUT-POLICY
Counters last updated 00:00:00 ago
Class-map: REALTIME (match-any)
845206 packets, 348763573 bytes
30 second offered rate 3000000 bps, drop rate 2500000 bps
Match: ip dscp cs5 (40) ef (46)
Priority: 10% (500 kbps), burst bytes 327265678, b/w exceed drops: 312925450

Class-map: DSCP-OUT-RTVI (match-any)
0 packets, 0 bytes
30 second offered rate 0000 bps, drop rate 0000 bps
Match: ip dscp af41 (0)

Queueing
queue limit 32 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
Class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: any

Queueing
queue limit 1024 packets
queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0

A. PE interface was not configured with enough bandwidth.
B. Traffic rate CE sent is over the SLA limit.
C. PE needs to upgrade to a higher throughput interface.
D. CE marked all traffic incorrectly to DSCP 46.
E. CE marked all traffic incorrectly to DSCP 46.
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
QUESTION 58
A service provider recently changed from RFC 3270 Uniform mode to Pipe mode. Which three considerations about this change are true? (Choose three.)
A. If the provider moved to a Short Pipe mode model, it would allow them to implement customer specific QoS policy on the PE egress.
B. The Pipe mode provides the isolation between the customer and provider DiffServ domains, while maintaining a simpler support model.
C. The Short Pipe mode derives the outbound classification of the WRED and WFQ based on the DiffServ policy of the provider.
D. In Uniform mode, when the topmost EXP value is changed, the changed EXP value will propagate to the original IP precedence or DSCP.
Correct Answer: ABD Section: (none) Explanation
Explanation/Reference:
http://www.cisco.com/en/US/tech/tk436/tk428/technologies_tech_note09186a008022ad7e.shtml
QUESTION 59
What would be the first step when defining an MQC?
A. Add one or more match commands to classify packets
B. Attach the traffic policy (policy map) to the interface by using the service-policy command
C. Define a traffic class by using the class-map command.
D. Apply the commands such as bandwidth, police, and set dscp to enable the QoS feature.
E. Create a traffic policy by using the policy-map command
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 60
Refer to the exhibit.

Which two statements are correct? (Choose two.)
A. The voice class is configured with the priority 128 command
B. The voice class is configured with the bandwidth 128 command.
C. The gold class is configured with the priority 100 command.
D. The gold class is configured with the bandwidth 100 command
E. The voice class is configured with the police 128 command.
Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Originally was A
QUESTION 61
Refer to the exhibit.

Which queueing method has been configured?
A. LLQ
B. CBWFQ
C. WFQ
D. MDRR
E. priority queueing
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
QUESTION 62
Which two Cisco IOS commands can be used to monitor QoS on a device? (Choose two.)
A. show class-map
B. show qos-maps
C. show policy-map
D. show service-policy
E. show qos-interface
F. show qos-dbl
Correct Answer: AC Section: (none) Explanation Explanation/Reference:
QUESTION 63
A service provider will apply this policy at which of these interfaces?
interface Gi1/1 service-policy output SP-POLICY ! policy-map SP-POLICY class TRAFFIC-CLASS-1 police rate percent 20 conform-action transmit exceed-action drop priority ! class TRAFFIC-CLASS-2 bandwidth percent 50 queue-limit 800 ms random-detect exp 3 280 ms 490 ms ! class class-default queue-limit 500 ms random-detect exp 1 200 ms 350 ms random-detect exp 0 100 ms 200 ms ! end-policy-map ! class-map match-any TRAFFIC-CLASS-1 match dscp ipv4 45 ef cs6 match mpls experimental topmost 5 6 end-class-map ! class-map match-any TRAFFIC-CLASS-2 match dscp ipv4 cs2 af21 af23 af31 af32 af33 35 37 match mpls experimental topmost 3 end-class-map !
A. CE interface toward PE
B. PE interface toward CE
C. PE interface toward P
D. P interface toward PE
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 64
Which three match statements are valid in Cisco IOS XR Software? (Choose three.)
A. match field
B. match mpls experimental topmost
C. match vpls
D. match flow
E. match qos-group
F. match port-type
Correct Answer: BCE Section: (none) Explanation
Explanation/Reference:
Fabric QoS policy class maps are restricted to matching a subset of the classification options. These are as follows:
.
precedence

.
dscp

.
qos-group

.
discard-class

.
mpls experimental topmost
To support QoS on a virtual private LAN service (VPLS)-enabled network, packets can be classified based on these VPLS-specific match criteria:
.
Match vpls broadcast

.
Match vpls known

.
Match vpls unknown

.
Match vpls multicast
QUESTION 65
Refer to the exhibit.

The QoS profile was recently updated to mark VoIP traffic with a DSCP setting of AF41. However, the traffic going to the phones in the 172.19.5.0/24 address space is not being marked properly. What is causing this problem?
A. The traffic policy is not written correctly, which causes the wrong marking to be applied.
B. The VoIP classification should be configured before any other classifications, because it is the highest priority.
C. The access list does not properly identify SIP traffic.
D. Class typeA markings appear first in the policy map, which causes this marking to be applied.
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
QUESTION 66
Refer to the exhibit.

Which two statements are correct? (Choose two.)
A. No traffic can be matched to the REALTIME traffic class.
B. No traffic can be matched to the VoIP traffic class
C. No traffic can be matched to the BULK-DATA traffic class.
D. AF11 or AF12 or AF13 marked packets will be matched to the BULK-DATA traffic class.
E. The BULK-DATA traffic class is missing the match-any option in the class-map command.
Correct Answer: AD Section: (none) Explanation
Explanation/Reference:
QUESTION 67
Refer to the exhibit.

A. This policy map is applied to the FastEthernet0/0 interface in the input direction.
B. No traffic matched the SP-REALTIME class.
C. A total of 133836 packets have been transmitted out of the FastEthernet0/0 interface.
D. Packets marked with both DSCP EF and MPLS EXP 5 markings will not be classified into the SP-REALTIME traffic class.
E. The FastEthernet0/0 interface is using CBWFQ egress queueing.
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 68
You work for service provider that employs a four-class service provider QoS model (best effort, bronze, silver, gold). A customer recently reported an issue with high drop rate on a missioncritical database application in the silver class. The silver class is currently at capacity. The gold class is currently only used for voice and video conferencing, and has available bandwidth. The application was remapped to the gold class. Which statements are valid alternative options to this decision? (Choose two.)
A. Moving to a three-class QoS model would allow for more bandwidth per class and would reduce the support of maintaining multiple classes.
B. The provider should consider moving to a six-class QoS model to provide more available classes of service to differentiate traffic.
C. In addition to the remapping, the provider would have to change the queue model from WFQ to priority queued
D. Additional bandwidth should have been added to the silver class from one of the lower classes before the traffic class was moved.
Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
QUESTION 69
Which three items are important when monitoring service quality in the SP network? (Choose three.)
A. The typical cause of QoS issues is intermittent failure of network devices and these are inherently difficult to detect.
B. QoS issues can be difficult to detect when there is not enough traffic to trigger the configured QoS policy.
C. Establishing alarm thresholds for QoS problems can be complicated.
D. QoS support differs from device to device, depending on underlying hardware platforms and software.
E. Collection of data to detect QoS issues is slow and labor-intensive
F. Troubleshooting class map configurations is complex and frequently required
Correct Answer: BCD Section: (none) Explanation
Explanation/Reference:
QUESTION 70
What are two benefits of the DiffServ model? (Choose two.)
A. Its class-based mechanisms are simple and scale well.
B. It provides absolute guarantees of service quality.
C. Service quality can be tailored to the needs of many different types of traffic.
D. It does not require setting up an end-to-end signaling mechanism.
Correct Answer: CD Section: (none) Explanation
Explanation/Reference:
QUESTION 71
Which three components would you use to define and apply traffic classification? (Choose three.)
A. route map
B. service policy
C. class map
D. route policy E. policy map
Correct Answer: BCE Section: (none) Explanation
Explanation/Reference:
QUESTION 72
Which Cisco IOS IP SLA Probe would you select to identify bottlenecks in the network?
A. ICMP Path Jitter
B. ICMP Echo
C. ICMP Path Echo
D. FTP Path Echo
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 73
When the customer LAN is managed by the service provider and the network is oversubscribed, what is the best location for use of congestion avoidance mechanisms?
A. on output interfaces from the customer LAN leading into the service provider network
B. in interfaces in the service provider network incoming from the customer LAN
C. in the service provider core
D. on output interfaces from the service provider network leading to the customer LAN
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
QUESTION 74
To classify and prioritize traffic according to importance, which three statements are correct? (Choose three.)
A. Each class should be guaranteed at least some bandwidth
B. Voice traffic should be given top priority.
C. Email should be placed in a best-effort class.
D. Critical applications should be given sufficient bandwidth to meet their requirements.
E. Video should be placed in the same class as voice.
Correct Answer: BCD Section: (none) Explanation
Explanation/Reference:
QUESTION 75
Which tool is best suited to provide incident management or trouble ticketing?
A. Remedy
B. CiscoWorks
C. Tivoli
D. Voyence
E. Intelliden
Correct Answer: A Section: (none) Explanation

QUESTION 76
Where would a service provider apply this policy?
interface Gi1/1 service-policy output SP-POLICY policy-map SP-POLICY class CLASS-REALTIME priority set cos 5 ! class CLASS-HIPRIORITY bandwidth remaining percent 75 set cos 3 ! class CLASS-BASIC bandwidth remaining percent 20 set cos 1 ! class class-default set cos 1 ! end-policy-map
class-map match-any CLASS-BASIC match dscp af11 af12 af13 end-class-map ! class-map match-any CLASS-REALTIME match dscp ef af42 af43 end-class-map ! class-map match-any CLASS-HIPRIORITY match dscp af21 af22 end-class-map
A. CE interface toward PE
B. PE interface toward CE
C. PE interface toward P
D. P interface toward PE
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
QUESTION 77
An MPLS VPN customer reports that the VoIP voice quality is very bad for calls across the MPLS VPN. What could be the problem?
A. Traffic shaping is applied to the voice traffic class
B. The voice traffic class is using the priority command.
C. The voice packets are marked as DSCP EF.
D. WRED is not configured for the voice traffic class.
E. The voice traffic class is using the default queue size.
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
QUESTION 78
A customer is experiencing poor quality on voice connections coming from a particular branch office. Data on the service provider network capacity indicates that the devices serving that location are heavily oversubscribed. It will be months before planned expansions can be implemented. Which class-based traffic-shaping technique would be appropriate to consider implementing?
A. shaping to the committed rate
B. shaping to the peak rate
C. shaping to the observed median rate
D. shaping to the configured average rate
Correct Answer: D Section: (none) Explanation Explanation/Reference:
QUESTION 79
A customer with an unmanaged CE router has reported experiencing poor quality on the video conferencing and broadcast multimedia applications. To address the issue, the provider has implemented shaping on the PE router to “smooth out” speed mismatches in the network. Which of these is a valid concern with this approach?
A. In addition to shaping, the provider should implement policing so the application can detect the congestion and throttle traffic.
B. Shaping can only be applied to the outbound interface, which does not prevent the customer from flooding the inbound link to the provider.
C. Shaping should only be used in a TCP-based environment where the application can detect the congestion and adjust. Shaping provides little benefit with UDP applications.
D. While shaping may help the broadcast multimedia application, it could cause additional delay in the video conferencing application.
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
QUESTION 80
Which two match statements are correct in Cisco IOS Software? (Choose two.)
A. class-map class1 match not protocol ip
B. class-map match-none class2 match protocol ip
C. class-map class3 match dscp af31 match dscp af41
D. class-map match-any class3 match dscp af31 match dscp af41
Correct Answer: AD Section: (none) Explanation
Explanation/Reference:
QUESTION 81
Refer to the exhibit.

You have implemented RFC 3270 Short Pipe mode in your MPLS network. A customer packet with the DSCP value of AF31 has been sent to the ingress PE router. The PE router has set the MPLS experimental bits per policy, but the policer has remarked the experimental bits of the top label. What will the DSCP value of the packet be when it leaves the egress PE router?
A. BE
B. CS1
C. CD3
D. CS4

E. AF31
Correct Answer: E Section: (none) Explanation
Explanation/Reference:
Short-Pipe mode is useful for ISPs implementing their own QoS policy independent of their customer’s QoS policy. The IP Precedence bits on an IP packet are propagated upward into the label stack as labels are added. When labels are swapped, the existing EXP value is kept. If the topmost EXP value is changed, this change is propagated downward only within the label stack, not to the IP packet.
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