Cisco 642-883 Exam Questions 2021

NEW QUESTION 1
DRAG DROP

Answer:

Explanation: L1 – R1 and R4 L1/L2 – R2 and R3 L2 – R5

NEW QUESTION 2
Which configuration implements the most secured OSPF authentication mode on Cisco IOS XE?

• A. interface Gi0/0/0/0ip ospf authentication message-digest ip ospf message-digest-key 1 md5 cisco
• B. router ospf 1 area 1authentication message-digest interface GigabitEthernet0/0/0/0 message-digest-key 1 md5 cisco
• C. router ospf 1 area 1interface GigabitEthernet0/0/0/0 authentication message-digest message-digest-key 1 md5 cisco
• D. router ospf 1area 1 authenticationinterface GigabitEthernet0/0/0/0 ip ospf authentication-key cisco
• E. interface Gi0/0/0/0 ip ospf authenticationip ospf authentication-key cisco

Answer: A

NEW QUESTION 3
DRAG DROP

Answer:

Explanation: Match the default Route – ipv4 prefix-list one permit 0.0.0.0/0 Match all routes – ipv4 prefix-list permit 0.0.0.0/0 le 32
Match any host routes - ipv4 prefix-list permit 0.0.0.0/32
Match any /25 to /32 prefixes - ipv4 prefix-list permit 0.0.0.0/0 ge 25

NEW QUESTION 4
An engineer is configuring an eBGP peering session. What is the default TTL value?

• A. 1
• B. 64
• C. 127
• D. 255

Answer: A

NEW QUESTION 5
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?

• A. extcommunity-set rt my-list 65000:1065000:2065000:30end-setroute-policy my-list ($med)if extcommunity rt matches-within my-list then set met $med
• B. extcommunity-set rt my-list 65000:1065000:2065000:30end-setroute-policy my-list ($med)if extcommunity rt matches-any my-list then set met $med
• C. extcommunity-set rt my-list 65000:1065000:2065000:30end-setroute-policy my-list ($med)if extcommunity rt matches-within my-list or med is $med is then set met $med
• D. extcommunity-set rt my-list 65000:1065000:2065000:30end-setroute-policy my-list ($med)if extcommunity rt matches-any my-list or med is $med then pass

Answer: B

NEW QUESTION 6
A service provider is deploying route redistributions for a large enterprise that wants to unify a few IGP routing domains into one to condense administration as well as common network and security policies. Which technique should be used to safely assume that the new routing domain is loop free?

• A. Enable filtering based on route-tagging on the redistribution points to avoid route- feedback.
• B. Define a static route to Null0 for all of the outgoing traffic on the redistribution points.
• C. Modify the metric associated with each redistributed prefix to implement loop-avoidance for inter-IGP routing domain designs.
• D. Disable the routing process on the interfaces with route-feedback potential on the redistribution points.

Answer: A

NEW QUESTION 7
What are two purposes of the BGP scan-time command? (Choose two.)

• A. to tune the BGP process which walks the BGP table and confirms the reachability of next hops
• B. to allow faster detection of downed BGP peers
• C. to improve BGP convergence time
• D. to tune the BGP update interval
• E. 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 <5-60>

NEW QUESTION 8
Which high-availability routing feature requires the neighbor router to support the graceful restart capability?

• A. BFD
• B. NSR
• C. NSF
• D. MTR

Answer: C

Explanation: On Cisco IOS XR software, NSF minimizes the amount of time a network is unavailable to its users following a route processor (RP) failover. The main objective of NSF is to continue forwarding IP packets and perform a graceful restart following an RP failover.
When a router restarts, all routing peers of that device usually detect that the device went down and then came back up. This transition results in what is called a routing flap, which could spread across multiple routing domains. Routing flaps caused by routing restarts create routing instabilities, which are detrimental to the overall network performance. NSF helps to suppress routing flaps in NSF-aware devices, thus reducing network instability.
NSF allows for the forwarding of data packets to continue along known routes while the routing protocol information is being restored following an RP failover. When the NSF feature is configured, peer networking devices do not experience routing flaps. Data traffic is forwarded through intelligent line cards while the standby RP assumes control from the failed active RP during a failover. The ability of line cards to remain up through a failover and to be kept current with the Forwarding Information Base (FIB) on the active RP is key to NSF operation.
When the Cisco IOS XR router running IS-IS routing performs an RP failover, the router must perform two tasks to resynchronize its link-state database with its IS-IS neighbors. First, it must relearn the available IS-IS neighbors on the network without causing a reset of the neighbor relationship. Second, it must reacquire the contents of the link-state database for the network.
The IS-IS NSF feature offers two options when configuring NSF:
•IETF NSF
•Cisco NSF
If neighbor routers on a network segment are NSF aware, meaning that neighbor routers are running a software version that supports the IETF Internet draft for router restartability, they assist an IETF NSF router that is restarting. With IETF NSF, neighbor routers provide
adjacency and link-state information to help rebuild the routing information following a failover.
In Cisco IOS XR software, Cisco NSF checkpoints (stores persistently) all the state necessary to recover from a restart without requiring any special cooperation from neighboring routers. The state is recovered from the neighboring routers, but only using the standard features of the IS-IS routing protocol. This capability makes Cisco NSF suitable for use in networks in which other routers have not used the IETF standard implementation of NSF

NEW QUESTION 9
Which router(s) is/are IS-Type L1/L2 IS-IS router?

• A. CE5 only
• B. PE6 only
• C. CE5 and PE6 only
• D. PE5 and PE6 only
• E. CE5, PE5 and PE6

Answer: D

Explanation: #show clns neighbor

NEW QUESTION 10
Which three valid session commands are supported by peer session templates? (Choose three.)

• A. local-as
• B. as-override
• C. inherit peer-session
• D. inherit peer-policy
• E. disable-connected-check
• F. route-reflector-client

Answer: ACE

NEW QUESTION 11
Which of the following is a characteristic of dual-multihomed connectivity between an enterprise network and the service provider network or networks?

• A. 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.
• B. Each service provider announces a default route on each of the links that connect to the customer with a different metric.
• C. An enterprise network announces a default route to each service provider.
• D. Load balancing can be achieved using the maximum-paths command.

Answer: A

NEW QUESTION 12
Refer to the exhibit.

XR1 must have XR4 as the primary exit point for only the first three subnets received from AS 100 and may not impact the rest of the subnets. Which configuration on XR1 is correct?

• A. prefix-set PREFER 100.100.100.0/30 le 32route-policy LPif destination in PREFER then set local-preference 200 endif
• B. route-policy LPif destination in (100.100.100.0/30 le 32) then set local- preference 200 else pass endif
• C. prefix-set PREFER 100.100.100.0/29 le 32route-policy LPif destination in PREFER then set local-preference 200 else pass endif
• D. route-policy LPif destination in (100.100.100.0/29 le 32) then set local preference 200 else set local-preference 100 endif

Answer: B

NEW QUESTION 13
In which network environment is IS-IS adjacency check important?

• A. in a multitopology environment where there are different instances of IS-IS running on the same router
• B. in an IPv4/IPv6 environment and running single-topology IS-IS
• C. when a level L1/L2 IS-IS router is neighboring with a Level 1 only or Level 2 only router
• D. when IS-IS neighbors are in an NBMA environment like over Frame Relay
• E. when IS-IS neighbors are in a broadcast environment like an Ethernet LAN

Answer: B

Explanation:
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NEW QUESTION 14
A Cisco IOS XR router must be configured with BFD for OSPF. Which configuration is correct?

• A. interface GigabitEthernet0/0/0/0 ip ospf bfd
• B. router ospf 1 area 0interface GigabitEthernet0/0/0/0 bfd fast-detect
• C. router ospf 1 area 0interface GigabitEthernet0/0/0/0 bfd fast-detect ipv4
• D. router ospf 1 bfd all-interfaces

Answer: B

NEW QUESTION 15
Refer to the exhibit.

R1 and XR2 cannot establish OSPF adjacency. Which option is the root cause of this issue?

• A. stub flag mismatch
• B. mismatched passwords
• C. process ID mismatch
• D. mismatched authentication types
• E. MTU mismatch

Answer: D

NEW QUESTION 16
Which series of commands configures area 1 as an OSPF totally stubby area on a Cisco IOS XR router?

• A. router ospfv3 1 router-id 10.10.10.1area 0interface GigabitEthernet 0/0/0/1 area 1stub no-summaryinterface GigabitEthernet 0/0/0/2
• B. router ospfv3 1 router-id 10.10.10.1default-information originate area 0interface GigabitEthernet 0/0/0/1 area 1stubinterface GigabitEthernet 0/0/0/2
• C. ipv6 prefix-list default permit ::0/0 router ospfv3 1router-id 10.10.10.1default-information originate area 0interface GigabitEthernet 0/0/0/1 distribute-list prefix-list default in area 1interface GigabitEthernet 0/0/0/2
• D. router ospfv3 1 router-id 10.10.10.1area 0interface GigabitEthernet 0/0/0/1area 1interface GigabitEthernet 0/0/0/2 no-summarypassive
• E. router ospfv3 1 router-id 10.10.10.1area 0interface GigabitEthernet 0/0/0/1 area 1stubinterface GigabitEthernet 0/0/0/2 default-cost 20

Answer: A

NEW QUESTION 17
Refer to the exhibit.

R1 is advertising subnets 1.1.1.X/32 via eBGP. XR4 must accept only the first seven subnets in its BGP table. Which configuration must occur on XR2 to meet these parameters?

• A. route-policy INBOUNDif destination in SUBNETS then pass endifrouter bgp 100 neighbor 10.10.14.1 address-family ipv4 unicast route-policy INBOUND in
• B. route-policy INBOUNDif destination in FILTER then pass endifrouter bgp 100 neighbor 10.10.14.1 address-family ipv4 unicast route-policy INBOUND in
• C. router bgp 100neighbor 10.10.14.1 address-family ipv4 unicast route-policy FILTER in
• D. router bgp 100neighbor 10.10.14.1 address-family ipv4 unicast route-policy SUBNETS in

Answer: B

NEW QUESTION 18
Refer to the Cisco IOS XE IS-IS configuration exhibit.

What are two problems with the configuration that are causing the IPv4, or the IPv6, or the IPv4 and IPv6 IS-IS operations to fail? (Choose two.)

• A. The configuration is missing the interface gi0/0 and interface gi0/0 commands under router isis 1.
• B. The configuration is missing the address-family ipv4 unicast and address-family ipv6 unicast commands under router isis 1.
• C. IPv6 unicast routing has not been enabled globally on the Cisco IOS XE router.
• D. The gi0/0 and gi0/1 interfaces are not participating in the router isis 1 routing instance.
• E. Multitopology IS-IS must be enabled to support both IPv4 and IPv6.
• F. Another router isis instance must be enabled to support IPv6.

Answer: CD

Explanation: http://www.cisco.com/en/US/docs/switches/metro/me3400/software/release/12.2_50_se/co
nfiguration/guide/swipv6.pdf
• When using user-network interface (UNI) or enhanced network interface (ENI) ports for any
IPv6-related features, you must first globally enable IP routing and IPv6 routing on the switch by entering the ip routing ipv6 unicast-routing

NEW QUESTION 19
For which reason might an enterprise’s Internet circuits use private AS BGP peerings?

• A. The enterprisewishes to obscure internal routing information from the Internet.
• B. The enterprise owns their own IP space.
• C. All redundant circuits are through the same provider.
• D. The enterprise uses BGP confederations internally.

Answer: C