Cisco 642-887 Online Practice Questions and Exam Preparation

Cisco 642-887 Online Questions & Answers

• Question 91:

  Which option describes the function of an IPv6 flow label?

  A. serves as a management flow to easily monitor any TCP/IP session running over IPv6
  B. serves as a 20-bit checksum per flow for authentication services built into IPv6
  C. enables efficient IPv6 flow classification based only on IPv6 main header fields
  D. used by MPLS when the service provider core network is fully IPv6 enabled
  C. enables efficient IPv6 flow classification based only on IPv6 main header fields

• Question 92:

  Which are typical class-based marking policies that are implemented on service provider IP NGN PE routers?

  A. On the PE ingress, classify the customer traffic and then mark with qos-group. On the PE egress, classify based on the qos-group and then mark with mpls exp.
  B. On the PE ingress, classify the customer traffic and then mark with mpls exp. On the PE egress, classify based on the mpls exp and then mark with qos-group.
  C. On the PE ingress, trust the customer QoS markings. On the PE egress, classify based on the customer QoS markings and then mark with qos-group.
  D. On the PE ingress, trust the customer QoS markings. On the PE egress, classify based on the customer QoS markings and then mark with mpls exp.
  A. On the PE ingress, classify the customer traffic and then mark with qos-group. On the PE egress, classify based on the qos-group and then mark with mpls exp.

• Question 93:

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

  A. Drop the packet.
  B. Transmit the packet.
  C. Set the CoS value and drop the packet.
  D. Set the DSCP value and drop the packet.
  E. Keep the packet in the buffer.
  F. Set the QoS group and drop the packet.
  A. Drop the packet.
  B. Transmit the packet.
  F. Set the QoS group and drop the packet.

• Question 94:

  Which driver uses an IntServ QoS model in an MPLS TE enabled service provider network?

  A. DSCP, which requires signaling across the provider network
  B. RSVP, which enables bandwidth guarantees across a provider network
  C. RSVP, which enables per-hop behavior across a provider network
  D. DSCP, which enables bandwidth guarantees across a provider network
  B. RSVP, which enables bandwidth guarantees across a provider network

• Question 95:

  What is the correct formula for determining the CIR?

  A. CIR = Bc/Tc
  B. CIR = Bc x Tc
  C. CIR = Tc/Bc
  D. CIR = Bc + Be
  E. CIR = Tc/(Bc+Be)
  F. CIR = (Bc+Be)/Tc
  A. CIR = Bc/Tc

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  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) ?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 96:

  Cisco MPLS TE path setup can be affected by which three tunnel attributes? (Choose three.)

  A. bandwidth
  B. delay
  C. MTU
  D. priority
  E. affinity
  A. bandwidth
  D. priority
  E. affinity

• Question 97:

  Refer to the exhibit.

  

  A network engineer who is working for an ISP wants to override the QoS that comes from the customer. The engineer wants to set a QoS value of 5 for all traffic. What are two reasons why the configuration is not working? (Choose two.)

  A. The service-policy command should point to the service policy, not to the class map
  B. The set command should reference CoS instead of MPLS EXP bits
  C. The service-policy configuration should be set as output
  D. The policy-map configuration needs to reference class-map Custom1
  E. The number 350 in the xconnect command should appear after the encapsulation type
  A. The service-policy command should point to the service policy, not to the class map
  D. The policy-map configuration needs to reference class-map Custom1

• Question 98:

  An engineer wants to implement constraint-based routing. Which MPLS application should the engineer use?

  A. unicast IP routing
  B. MPLS VPN
  C. MPLS TE
  D. RSVP
  C. MPLS TE

• Question 99:

  Scenario: 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
  C. 16024

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  Explanation: Issue on PE8: show mpls forwarding-table Look for the "Outgoing Label" not the "Local Label" for the prefix 10.7.1.1/32. You will notice that the Label value is 16024.

• Question 100:

  Which three commands are used to troubleshoot why IP packets are not forwarded on the LSP? (Choose three.)

  A. show cef prefix/length to check the prefix information
  B. debug mpls ldp transport events to display events related to the LDP peer discovery mechanism
  C. show mpls forwarding labels hardware egress location to check the hardware label FIB
  D. show arp location for the next hop prefix
  E. show mpls ldp discovery for the corresponding label information
  F. debug mpls ea platform all to display MPLS setup events and errors
  A. show cef prefix/length to check the prefix information
  C. show mpls forwarding labels hardware egress location to check the hardware label FIB
  D. show arp location for the next hop prefix