642-887 Implementing Cisco Service Provider Next-Generation Core Network Services

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Question 1


On PE7 which statement is correct regarding the "traffic-policing" policy-map?

  • A. The "traffic-policing" QoS policy is applied to the Gi0/0/0/0 interface in the outbound direction.
  • B. The "traffic-policing" QoS policy will police the traffic matched by the "test12" ACL to 3 mbps and will drop all exceeding traffic.
  • C. All incoming traffic not matched by the "test12" ACL to the Gi0/0/0/0 interface will be dropped.
  • D. The "traffic-policing" QoS policy is using dual rate class-based traffic policing.

Answer : B

Explanation: #show running-config policy-map #show policy-map

Question 2

Which three statements are correct regarding a Cisco MPLS TE? (Choose three.)

  • A. A Cisco MPLS TE tunnel maps onto an LSP path.
  • B. Tunnels are bidrectional by default.
  • C. Packets that are mapped into a Cisco MPLS TE tunnel will have two labels, with the top label indicating what the tail-end router should do with the packet.
  • D. A tunnel that is created with a priority of 0 can pre-empt an existing tunnel with a priority of 7.
  • E. CBR takes into account link resource and traffic tunnel attributes.
  • F. RSVP is used between customer routers.

Answer : A,D,E

Question 3

Which two fields are in the traffic engineering topology database? (Choose two.)

  • A. TE-metric
  • B. IGP metric
  • C. link delay
  • D. LSP setup priority
  • E. LDP authentication

Answer : A,D

Question 4

Which two characteristics describe the difference between MPLS QoS pipe and short-pipe
models? (Choose two)

  • A. Short-pipe mode does not need MPLS usage, but pipe mode does.
  • B. In short-pipe mode, the egress LSR uses the tunneled PHB marking, but in pipe mode, the egress LSR uses the LSP PHB marking.
  • C. Pipe mode does guarantee that the tunneled packet marking remains unchanged, but short-pipe does not.
  • D. In short-pipe mode, the egress LSR uses the LSP PHB marking, but in pipe mode, the egress LSR uses the tunneled PHB marking.
  • E. Short-pipe mode can be implemented on MPLS networks regardless of the MPLS PHP mechanism usage.

Answer : B,E

Question 5


From PE8 router, what is the label action used to reach the P2 loopback 0 interface

  • A. Swap label 35 with label 16004
  • B. Push label 16004
  • C. Pop label 35
  • D. Pop label 16009
  • E. Push Label 16009
  • F. Swap label 35 with label 16009

Answer : C

Explanation: show mpls forwarding-table , find prefix and you will see there under outgoing Label "Pop Label" (This is actually logic because the prefix is directly connected and therefore the packet will forward without label). If the router should forward any packet to that prefix, the packet should be received with Local label on PE8 (Local Label = 35), the router will remove it and forward it without Label.

Question 6

Which item is not available to be used for QoS classification in Cisco IOS XR?

  • A. MAC SA
  • B. protocol
  • C. inner EXP
  • D. discard-class
  • E. QoS-group
  • F. VLAN

Answer : C

Question 7

A network engineer must design a core network routing domain that supports Cisco MPLS
TE. Which two interior gateway protocols represent viable solutions? (Choose two.)

  • A. Routing Information Protocol version 2
  • B. Open Shortest Path First
  • C. Enhanced Interior Gateway Routing Protocol
  • D. Intermediate-System to Intermediate-System
  • E. Border Gateway Protocol

Answer : B,D

Question 8

Refer to the exhibit. XR2 needs to have LDP configured with PE1. Which configuration
achieves this goal?

  • A. interface giga 0/0 Mpls ip exit commit
  • B. router ospf 1 mpls ldp auto config area 0 exit commit
  • C. router ospf 1 area 0 mpls ldp auto config exit commit
  • D. interface giga 0/1 mpls ldp exit commit

Answer : C

Question 9


From the PE8 router, how many total prefixes for have an incoming local label assigned
(including the imp-null)?

  • A. 45
  • B. 21
  • C. 66
  • D. 22

Answer : B

Explanation: On PE8 issue: show mpls ip binding summary and look at "assigned in labels". That value is the correct answer NOT "learned out label".

Question 10

Which three statements are correct regarding ping mpls command operations? (Choose

  • A. MPLS OAM has to be enabled on the router using the mpls oam command.
  • B. They use a 127/8 address as the destination address in the MPLS echo request packet.
  • C. They use ICMP echo request and ICMP echo reply packets.
  • D. They are used to test for a broken LSP.
  • E. If there is a broken LSP, instead of using label switching, the packet can still be forwarded based on the destination IP address in the mpls ping echo request packet.

Answer : A,B,D

Explanation: How MPLS Ping works? MPLS Ping doesnt rely on ICMP echo messages. Instead it uses UDP protocol with both source and destination port as 3503 and relies on MPLS Echo request and MPLS Echo reply. When MPLS ping is triggered from any MPLS router, it will generate UDP segment with source/destination port as 3503. The source address will be selected as usual while the destination address will be The IP TTL will be set to 1. Below is a sample IP format when MPLS Ping is originated from R5 to,

Now the originating LSR will look into the LFIB and populate the label header with respective labels to reach the FEC, in our case R4 on receiving the MPLS packet will be able to send to the actual destination only if the LSP is end to end. If the LSP is broken between R4 and R6, R4 will look into the destination IP address which will be and wont be able to perform IP forwarding. As per RFC 1812, a router should not forward any packet that has destination address of

Question 11

Answer :

Question 12

A DSCP value of 41 in decimal corresponds to which IP precedence value?

  • A. 3 – Flash
  • B. 4 – Flash Override
  • C. 5 – Critical
  • D. 6 – Internet Control
  • E. 7 – Network Control

Answer : C

Explanation: = INT(41/8) The AF behavior group defines four separate AF classes with Class 4 having the highest priority. Within each class, packets are given a drop precedence (high, medium or low). The combination of classes and drop precedence yields twelve separate DSCP encodings from AF11 through AF43 (see table)

Question 13

Which two of the following statements are correct regarding LSPs? (Choose two.)

  • A. An LSP is created for every routing protocol entry.
  • B. Each LSP is bidirectional, that is, packets traveling in the opposite direction use the same LSP.
  • C. An IGP is used to populate routing tables in all routers in an MPLS domain.
  • D. LDP is used to propagate labels and build LSPs.
  • E. The FIB is used to forward MPLS-labeled packets down an LSP.

Answer : C,D

Question 14

A network engineer must make a reservable maximum bandwidth of 75 Mbps on a Cisco
ASR 9000 series router. Which configuration satisfies this requirement in Cisco IOS XR?

  • A. 2802_FY14Q4_CORE_Q33_o1
  • B. 2813_FY14Q4_CORE_Q33_o2
  • C. 2824_FY14Q4_CORE_Q33_o3
  • D. 2835_FY14Q4_CORE_Q33_o4

Answer : C

Question 15

Which three network services can be implemented using MPLS within the service provider
IP NGN core? (Choose three.)

  • A. Layer 2 VPNs
  • B. Layer 3 VPNs
  • C. traffic engineering
  • D. IntServ traffic engineering tunnels
  • E. encrypted LSPs

Answer : A,B,C

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