[Free] 2019(Nov) EnsurePass Cisco 642-883 Dumps with VCE and PDF 1-10

Get Full Version of the Exam
http://www.EnsurePass.com/642-883.html

Question No.1

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: AC

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.2

Refer to the exhibit. XR4 must be configured to advertise only AS 100 local subnets to AS 10. Which configuration on XR4 achieves this goal?

image

  1. as-path-set LOCAL ios-regex ^$

    route-policy ADV

    if as-path in LOCAL then pass endif

  2. as-path-set LOCAL ios-regex #39;^100$#39; route-policy ADV

    if as-path in LOCAL then pass endif

  3. as-path-set LOCAL ios-regex #39;^$#39;

    route-policy ADV

    if as-path in LOCAL then pass endif

  4. as-path-set LOCAL ios-regex ^100$ route-policy ADV

if as-path in LOCAL then pass endif

Answer: C

Question No.3

When using the Cisco IOS-XR show bgp command to examine the BGP table, the Metric value being displayed is used to represent which BGP attribute?

  1. Weight

  2. Local Preference

  3. MED

  4. Cost Community

Answer: C

Question No.4

In an AS with 10 routers running IBGP, how many IBGP sessions will be required to establish fully meshed IBGP peerings?

A.

10

B.

20

C.

45

D.

50

E.

99

F.

100

Answer: C

Question No.5

In a Cisco IOS XR OSPF NSF operation, which option is the result of a segment without NSF- capable peers?

  1. NSF is disabled on all segmentson any linecard that has a non-NSF-capable neighbor.

  2. NSF capabilities for that segment are disabled.

  3. NSF operates in unidirectional mode for that segment.

  4. NSF is disabled globally on the router.

Answer: B

Question No.6

An engineer is using configuration blocks to build policy-based routing. All other traffic must not be affected and the policy must be applied to GigabitEthernet1/0. Which block correctly implements traffic that is destined for 10.10.10.0/24 using a next hop of 192.168.55.1?

  1. access-list 110

    permit ip any 10.10.10.0 0.0.0.255 route-map PBR permit 10

    match ip address 110

    set next-hop 192.168.55.1

    interface GigabitEthernet1/0 ip policy route-map PBR

  2. access-list 110

    permit ip any 10.10.10.0 0.0.0.255 route-map PBR permit 10

    match ip address 110

    set next-hop 192.168.55.1 route-map PBR permit 20 interface GigabitEthernet1/0 ip policy route-map PBR

  3. access-list 110

    permit ip any 10.10.10.0 255.255.255.0 route-map PBR permit 10

    match ip address 110

    set next-hop 192.168.55.1 interface GigabitEthernet1/0 ip policy route-map PBR

  4. access-list 110

permit ip any 10.10.10.0 255.255.255.0 route-map PBR permit 10

match ip address 110

set next-hop 192.168.55.1 route-map PBR permit 20 interface GigabitEthernet1/0 ip policy route-map PBR

Answer: B

Question No.7

You are implementing OSPF as the IGP using a single OSPF area design. The router memory usage for OSPF is too high. Which two methods can lower the OSPF memory usage? (Choose two.)

  1. Enable OSPF synchronization

  2. Implement multi-area OSPF

  3. Enable OSPF sham links to reduce the number of LSAs

  4. Implement route summarization on the ABRs

  5. Enable route leaking between Level 1 and Level 2 areas

Answer: BD

Question No.8

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.9

Which two methods implement high availability in OSPF on Cisco IOS XR? (Choose two.)

  1. NSF

  2. NSR

  3. BFD

  4. fast hellos

  5. sham-links

Answer: AB

Question No.10

An engineer wants to define a route policy that sets MED to a given value in case the extended community attributes of a network prefix match at least one of the values:

65000:10, 65000:20, or 65000:30.

Which configuration accomplishes this task?

  1. extcommunity-set rt my-list 65000:10

    65000:20

    65000:30

    end-set

    route-policy my-list ($med)

    if extcommunity rt matches-within my-list then set met $med

  2. extcommunity-set rt my-list 65000:10

    65000:20

    65000:30

    end-set

    route-policy my-list ($med)

    if extcommunity rt matches-any my-list then set met $med

  3. extcommunity-set rt my-list 65000:10

    65000:20

    65000:30

    end-set

    route-policy my-list ($med)

    if extcommunity rt matches-within my-list or med is $med is then set met $med

  4. extcommunity-set rt my-list 65000:10

65000:20

65000:30

end-set

route-policy my-list ($med)

if extcommunity rt matches-any my-list or med is $med then pass

Answer: B

Get Full Version of the Exam
642-883 Dumps
642-883 VCE and PDF