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2017 Nov Cisco Official New Released 642-887
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Implementing Cisco Service Provider Next-Generation Core Network Services

Question No: 81

Which option is a Cisco-recommended congestion management or queuing method for real-time traffic for voice and video?

  1. CB-WFQ

  2. PQ

  3. WFQ

  4. LLQ

Answer: D

Question No: 82 DRAG DROP

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Answer:

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Question No: 83

When implementing MPLS TE tunnels on Cisco IOS XR routers, what is the tunnel setup and hold priority value range, and which value has the highest priority?

  1. 0-63, where 0 is the highest priority

  2. 0-63, where 63 is the highest priority

  3. 0-7, where 0 is the highest priority

  4. 0-7, where 7 is the highest priority

Answer: C

Question No: 84

When defining an explicit MPLS TE tunnel path, which two command options are available under the explicit-path configuration mode? (Choose two.)

  1. exclude-address

  2. include-address

  3. next-address

  4. dynamic-address

Answer: A,C

Question No: 85

Scenario:

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Dumps4Cert 2017 PDF and VCE

Dumps4Cert 2017 PDF and VCE

Dumps4Cert 2017 PDF and VCE

On the PE8-router what is the label value used to reach the 10.7.1.1/32 network prefix?

A. 10.0.2.1:0

B. imp-null C. 16024 D. 128

Answer: C

Explanation: Issue on PE8: show mpls forwarding-table

Look for the quot;Outgoing Labelquot; not the quot;Local Labelquot; for the prefix 10.7.1.1/32. You will notice that the Label value is 16024.

Question No: 86

Which option is the appropriate way to configure a color-aware, dual-rate policer together with a color-blind, single-rate policer for the rest of the traffic?

  1. class-map match-all CLASS1

    match dscp af31

    class-map match all CLASS2 match dscp af32

    class-map match-all CLASS3 match dscp ef

    policy-map POLICY1 class CLASS1

    police rate 100000 peak-rate 200000

    conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af11

    exceed-action set-dscp-transmit af21 violate-action set-dscp-transmit af23

  2. class-map match-all CLASS 1 match dscp af31

    class-map match-all CLASS2 match dscp af32

    class-map match-all CLASS3 match dscp af33

    policy-map POLICY1 class CLASS1

    police rate 100000 burst 31250

    conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af11

    exceed-action set-dscp-transmit af21 violate-action set-dscp-transmit af23

  3. class-map match-all CLASS 1 match dscp af31 af32 af33

    class-map match-all CLASS2 match dscp af32

    class-map match-all CLASS3 match dscp af33

    policy-map POLICY1 class CLASS1

    police rate 100000 burst 31250

    conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af31

    exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit af33 class class-default

    police rate percent 10 peak-rate percent 30

  4. class-map match-all CLASS 1 match dscp af31 af32 af33

    class-map match-all CLASS2 match dscp af32

    class-map match-all CLASS3 match dscp af33

    policy-map POLICY1 class CLASS1

    police rate 100000 peak-rate 200000

    conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af31

    exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit af33 class class-default

    police rate percent 10 peak-rate percent 30

  5. class-map match-all CLASS 1 match dscp af31 af32 af33

class-map match-all CLASS2 match dscp af32

class-map match-all CLASS3 match dscp af33

policy-map POLICY1 class CLASS1

police rate 100000 peak-rate 200000

conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af31

exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit af33 class class-default

police rate 10000

Answer: E

Question No: 87

What is the correct formula for determining the CIR?

  1. CIR = Bc/Tc

  2. CIR = Bc x Tc

  3. CIR = Tc/Bc

  4. CIR = Bc Be

  5. CIR = Tc/(Bc Be)

  6. CIR = (Bc Be)/Tc

Answer: A Explanation:

Committed Information Rate (CIR) – the rate the device will send at (on average) over a one second period.

The default CIR when traffic-shaping is enabled on the interface is 56K. CIR is also referred to as the “target rate”. Since the device is forced to send at the AR, it does not send all of the time (within one second) 脗 in order to send an average amount of data that equals the CIR.

Minimum CIR (mincir) – the rate the service provider guarantees to accept. Theoretically, the provider will set the DE bit for all traffic above this rate. Mincir is designed to be used in conjunction with adaptive shaping. With adaptive shaping, the router will throttle down in the event of congestion. The router will not throttle down below this value.

Committed Burst (Bc) – the number of committed bits allows to be sent during a given interval. The device sends an average amount of traffic to achieve the CIR. The Bc value defaults to 1/8 of the configured CIR for speeds below 650K. For speeds above that, it is roughly 1/16 of CIR.

Excess Burst (Be) – the number of non-committed bits the router is allowed to send above Bc during the first interval (Tc). The amount of Be “credits” is derived from unused Bc credits in previous intervals. There is no limit to how long Be can “store” unused Bc credits. It is a common misconception that Be can only store credits from the previous interval or the previous second. There is no default Be value.

Committed Rate Measurement Interval (Tc) – the time interval over whic Bc or Bc Be can be transmitted. The max value is 125 ms and the minimum value is 10 ms.

The Formula

CIR, Tc, and Bc are related mathematically by the following formula:

CIR = Bc/(Tc/1000) Notice the division of Tc by 1000 is used to convert milliseconds into seconds – the common measurement of CIR and Bc.

Question No: 88

The Cisco IOS and IOS XE qos pre-classify command allows which kind of packet classification on IP packets that are encapsulated with GRE and IPsec?

  1. allows for packets to be classified based on the ToS byte values before packet encryption

  2. allows for packets to be classified based on the ToS byte values after packet encryption

  3. allows for packets to be classified based on the packet payload before packet encryption

  4. allows for packets to be classified based on the packet payload after packet encryption

  5. allows for packets to be classified based on the packet header parameters other than

the ToS byte values after packet encryption

Answer: A Explanation:

http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a008017405e. shtml

The qos pre-classify command

When packets are encapsulated by tunnel or encryption headers, QoS features are unable to examine the original packet headers and correctly classify the packets. Packets traveling across the same tunnel have the same tunnel headers, so the packets are treated identically if the physical interface is congested. With the introduction of the Quality of Service for Virtual Private Networks (VPNs) feature, packets can now be classified before tunneling and encryption occur.

In this example, tunnel0 is the tunnel name. The qos pre-classify command enables the QoS for VPNs feature on tunnel0:

Router(config)# interface tunnel0

Router(config-if)# qos pre-classify

Question No: 89

Which three options can an engineer select for a traffic policer in case the traffic rate is less than the conform burst? (Choose three.)

  1. Drop the packet.

  2. Transmit the packet.

  3. Set the CoS value and drop the packet.

  4. Set the DSCP value and drop the packet.

  5. Keep the packet in the buffer.

  6. Set the QoS group and drop the packet.

Answer: A,B,F

Question No: 90

According to the Intserv model, which two options are traffic-specific parameters? (Choose two.)

  1. token bucket

  2. calculated average queue size

  3. minimum policed unit

  4. traffic marking

  5. rate policing

Answer: A,C

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