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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: 71

Which four options describe the functions of the control world in an AToM environment? (Choose four.)

  1. It carries generic and Layer 2 payload-specific information.

  2. It prevents fragmentation and reassembly.

  3. It preserves the sequence of the transported frames.

  4. It is responsible for padding all packets.

  5. It is responsible for padding the small packets.

  6. It enables proper load balancing without packet desequencing independent of L2VPN packet content.

  7. It enables an optimal path for the L2VPN packet content to follow through the MPLS backbone.

  8. It carries Layer 2 payload-specific information.

Answer: A,C,E,F

Question No: 72

When configuring class-based WRED on Cisco routers, which WRED parameter is not user configurable on a Cisco IOS XR but is user configurable on a Cisco IOS and IOS XE?

  1. the ingress or egress direction where the class-based WRED policy will be applied

  2. the maximum threshold

  3. the minimum threshold

  4. the mark probability denominator

Answer: D Explanation:

Comparison of Cisco IOS QoS and Cisco IOS-XR QoS

The Cisco IOS-XR software implementation of QoS is basically the same as the QoS implementation on Cisco

IOS software, with the following exceptions:

鈥n Cisco IOS-XR software, the bandwidth command can be configured only in egress policies.

鈥he following changes have been made to the class-map command on Cisco IOS-XR software:

-Supports 4K per logical router.

-Maximum number of match criteria configurable in one class map is eight.

鈥hen a class is marked as high priority using the priority command on Cisco IOS-XR software, we recommend that you configure a policer to limit the priority traffic. Limiting the priority traffic will ensure that the priority traffic does not starve all of the other traffic on the line card. Use the police command to explicitly configure the policer.

鈥n Cisco IO-XR software, only one conform-action, exceed-action, or violate-action command can be configured at a time. To configure traffic policing, use the police command.

鈥n Cisco IOS-XR software, policy modifications cannot be made on existing policies. Use the policy-map command to remove the policy from all attached interfaces, delete the policy map, and redefine a new policy.

鈥hen configuring a policy map on Cisco IOS-XR software, the maximum number of classes configurable in one policy map is 16, which includes both Level 1 and Level 2 classes. To configure a policy map, use the policy-map command.

鈥hen WRED is configured on Cisco IOS-XR software, the mark probability in the random- detect command is not configurable-it is always set to 1.

鈥hen the random-detect exp command is used on Cisco IOS-XR software, the exponential weighting constant is not configurable and will be programmed automatically by Cisco IOS-XR software.

鈥hen access control lists (ACLs) are used in QoS class maps, the underlying deny or permit actions associated with access control entries (ACEs) are ignored. ACEs are used as a classification mechanism in order to provide appropriate QoS behavior as specified in class maps. Use ACLs that include ACEs with permit actions only.

Question No: 73

Which two statements are correct in describing ISP environments that are running IP/MPLS in the core network? (Choose two.)

  1. On the PE routers, each BGP route must use a unique label to reach the BGP next hop.

  2. The BGP next hops point to the PE routers, and only the PE routers are required to run BGP.

  3. A full mesh of IBGP sessions are required between all of the PE and P routers to ensure proper packets forwarding.

  4. The PE and P routers run LDP to learn the labels for reaching the BGP next-hop addresses.

Answer: B,D

Question No: 74

Which three steps are required to configure QPPB on Cisco IOS XR routers? (Choose three.)

  1. Apply a QPPB route policy to the BGP process using the table-policy command

  2. Apply a QPPB route policy to the BGP neighbor using the route-policy command

  3. Define a QPPB route policy to match the customer routes, then set the IP precedence or qos-group

  4. Define a QPPB route policy to match the customer IP precedence or qos-group markings, then set the BGP community

  5. Enable QPPB on an interface using the ipv4 bgp policy propagation input ip- precedence|qos-group destination|source command

  6. Enable QPPB on an interface using the ipv4 bgp policy propagation output ip- precedence|qos-group destination|source command

Answer: A,C,E

Explanation:

QoS Policy Propagation via BGP (QPPB), is a mechanism that allows propagation of quality of service (QoS) policy and classification by the sending party based on access lists, community lists and autonomous system paths in the Border Gateway Protocol (BGP), thus helping to classify based on destination instead of source address.

Question No: 75

On Cisco routers, which three methods can be used to map traffic into the MPLS traffic engineering tunnel? (Choose three.)

  1. on-demand routing

  2. static routing

  3. optimized edge routing

  4. policy-based routing

  5. autoroute

Answer: B,D,E

Question No: 76

What are the four fields inside the MPLS shim header? (Choose four.)

  1. EXP

  2. TTL

  3. Version

  4. S

  5. Length

  6. Label

  7. Type

  8. FCS

Answer: A,B,D,F

Question No: 77

Which two network devices are trusted endpoints in a network? (Choose two.)

  1. video endpoint

  2. PC

  3. wireless clients

  4. IP phone

Answer: A,D

Question No: 78

Which affinity value will be matched by the affinity bit mask of the affinity 0xFF00000A mask 0xFFFF000F command?

  1. 0xFFFF000A

  2. 0xFF00EEEA C. 0xFF000000 D. 0x00000000 E. 0x11110001

Answer: B Explanation:

0xFF00000A 11111111000000000000000000001010

0xFFFF000F 11111111111111110000000000001111

0xFF00EEEA 11111111000000001110111011101010

Question No: 79

Which method is used to mark traffic matched by class-map MY_CLASS as Expedited Forwarding?

  1. set ip dscp cs7

  2. set dscp cs7

  3. set dscp 46

  4. set dscp 45

Answer: C

Question No: 80

Which Cisco IOS XR command should be used to identify if MPLS TE FRR is enabled?

  1. show mpls traffic-eng tunnel lt;tunnel#gt;

  2. show mpls frr

  3. show mpls traffic-eng protection

  4. show mpls protection

  5. show mpls fast-reroute

Answer: A Explanation:

The MPLS Traffic Engineering (TE)-Fast Reroute (FRR) Link and Node Protection feature provides link protection (backup tunnels that bypass only a single link of the label-switched path (LSP)), node protection (backup tunnels that bypass next-hop nodes along LSPs), and the following FRR features:

鈥ackup tunnel support

鈥ackup bandwidth protection

鈥esource Reservation Protocol (RSVP) Hellos

Prerequisites for MPLS Traffic Engineering (TE)-Fast Reroute (FRR) Link and Node Protection

Your network must support the following Cisco IOS features:

鈥P Cisco Express Forwarding

鈥ultiprotocol Label Switching (MPLS)

Your network must support at least one of the following protocols:

鈥ntermediate System-to-Intermediate System (IS-IS)

鈥pen Shortest Path First (OSPF)

Before configuring FRR link and node protection, it is assumed that you have done the following tasks but you do not have to already have configured MPLS TE tunnels:

鈥nabled MPLS TE on all relevant routers and interfaces

鈥onfigured MPLS TE tunnels

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