642-883 Latest Exam (Aug 2018)

[Free] 2018(Aug) Dumps4cert Cisco 642-883 Dumps with VCE and PDF Download 41-50

August 13, 2018

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Deploying Cisco Service Provider Network Routing (SPROUTE)

Question No: 41

Refer to the Cisco IOS XR route policy exhibit.

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If the original incoming routing update has an MED of 10 and a local preference of 100, how will the routing update be modified?

  1. The local preference will be set to 100, the MED will be set to 10, and the weight will be set to 100.

  2. The local preference will be set to 100, the MED will be set to 10, and the weight will be set to 200.

  3. The local preference will be set to 200, the MED will be set to 10, and the weight will be set to 100.

  4. The local preference will be set to 200, the MED will be set to 10, and the weight will be set to 200.

Answer: C

Question No: 42

A network specialist is working for a large enterprise that has a BGP-enabled multihomed core infrastructure. Recently, the ISP that provides Internet connectivity to the company had to temporarily disable one of the BGP sessions as a result of routers blackholing BGP prefixes in transit. Which option can the specialist use to avoid this incident in the future?

  1. filtering local prefixes outbound

  2. using only one router as primary BGP speaker

  3. permitting only local prefixes outbound

  4. filtering external prefixes inbound

Answer: C

Question No: 43

What are two purposes of the BGP scan-time command? (Choose two.)

  1. to tune the BGP process which walks the BGP table and confirms the reachability of next hops

  2. to allow faster detection of downed BGP peers

  3. to improve BGP convergence time

  4. to tune the BGP update interval

  5. to decrease the effects of unstable routes by increasing the route suppression time

Answer: A,C Explanation:

http://www.networkers-online.com/blog/2008/12/bgp-performance-tunning-convergence- stability-scalabilityand-nsf-part-2/

Background BGP scanner

It is responsible for BGP housekeeping by scanning both the BGP RIB and the IP RIB and cleaning and sorting things out.

BGP monitors the next hop of the installed routes to verify next-hop reachability and to select, install, and validate the BGP best path. By default, the BGP scanner polls the RIB for this information every 60 seconds.

During the 60 second time period between scan cycles, IGP instabilities or other network failures can cause temporarily black holes and routing loops.

NOTE With Cisco IOS the default timer is 60 seconds for the IPv4 address family and 15 seconds for the

VPNv4 address family in order to optimize the VPNs routing table convergence. This timer can be controlled via the following command:

Router(config-router)#bgp scan-time lt;5-60gt;

Question No: 44

Which statement best describes the function of a BGP af-group?

  1. Use templates in different neighbors so it makes the BGP implementation easier.

  2. Group different address family neighbors inside BGP.

  3. Create a group of neighbors that can inherit address family configuration inside BGP.

  4. Substitute the class maps inside BGP on Cisco IOS XR devices.

Answer: B

Question No: 45

Which OSPF feature allows a router with redundant route processors to maintain its OSPF state and adjacencies across planned and unplanned RP switchovers and does this by checkpointing state information from OSPF on the active RP to the standby RP? This feature does not require the OSPF neighbor to support graceful restart.

  1. NSR

  2. NSF

  3. BFD

  4. MTR

  5. SDR

Answer: A Explanation: Continuous Forwarding

An important aspect of high availability is maintenance of traffic forwarding, even in the

case of control-plane switchovers. Cisco IOS XR Software has several built-in features that can provide continuous forwarding, including RSP stateful switchover (SSO), Nonstop Forwarding (NSF), Graceful Restart, and NSR.

NSF: Cisco IOS XR Software supports forwarding without traffic loss during a brief outage of the control plane through signaling and routing protocol implementations for Graceful Restart extensions as standardized by the IETF. In addition to standards compliance, this implementation has been compatibility tested with Cisco IOS Software and third-party operating systems.

Graceful Restart: This control-plane mechanism ensures high availability by allowing detection and recovery from failure conditions while preserving NSF services. Graceful Restart is a way to recover from signaling and control-plane failures without affecting the forwarding plane. Cisco IOS XR Software uses this feature and a combination of check pointing, mirroring, RSP redundancy, and other system resiliency features to recover prior to timeout and avoid service downtime as a result of network reconvergence.

NSR: This feature allows for the forwarding of data packets to continue along known routes while the routing protocol information is being refreshed following a processor switchover.

NSR maintains protocol sessions and state information across SSO functions for services such as Multiprotocol Label Switching (MPLS) VPN. TCP connections and the routing protocol sessions are migrated from the active RSP to the standby RSP after the RSP failover without letting the peers know about the failover. The sessions terminate locally on the failed RSP, and the protocols running on the standby RSP reestablish the sessions after the standby RSP goes active, without the peer detecting the change. You can also use NSR with Graceful Restart to protect the routing control plane during switchovers. The Cisco IOS XR Operating System provides system resiliency through a comprehensive set of high-availability features including modularity, process restart, fault handling, continuous forwarding, and upgradability.

Question No: 46

Refer to the exhibit.

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Area 1 routers must have only a default route in their OSPF routing tables. Which configuration must be completed on XR2 to meet this requirement?

  1. router ospf 1 address-family ipv4

    interface GigabitEthernet0/0/0/1 area 1 stub no-summary

  2. router ospf 1

    area 1 stub no-summary

  3. router ospf 1 area 1 stub

    interface GigabitEthernet0/0/0/1

  4. router ospf 1

area 1 stub no-summary interface GigabitEthernet0/0/0/1

Answer: D

Question No: 47

Which of the following is a characteristic of dual-multihomed connectivity between an enterprise network and the service provider network or networks?

  1. An enterprise network that is connected to two or more different service providers with two or more links per service provider and using BGP to exchange routing updates with the service providers.

  2. Each service provider announces a default route on each of the links that connect to the customer with a different metric.

  3. An enterprise network announces a default route to each service provider.

  4. Load balancing can be achieved using the maximum-paths command.

Answer: A

Question No: 48

Which option is where BGP graceful restart is negotiated between peers?

  1. open message

  2. keep-alive message

  3. notification message

  4. update message

Answer: A

Question No: 49

Which configuration implements the most secured OSPF authentication mode on Cisco IOS XE?

  1. interface Gi0/0/0/0

    ip ospf authentication message-digest ip ospf message-digest-key 1 md5 cisco

  2. router ospf 1 area 1

    authentication message-digest interface GigabitEthernet0/0/0/0 message-digest-key 1 md5 cisco

  3. router ospf 1 area 1

    interface GigabitEthernet0/0/0/0 authentication message-digest message-digest-key 1 md5 cisco

  4. router ospf 1

    area 1 authentication

    interface GigabitEthernet0/0/0/0 ip ospf authentication-key cisco

  5. interface Gi0/0/0/0 ip ospf authentication

ip ospf authentication-key cisco

Answer: A

Question No: 50 DRAG DROP

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