Top Quality 642-883 Free Practice Questions 2021

NEW QUESTION 1
When configuring BGP on Cisco IOS XR Software, which address-family is enabled by default?

• A. IPv4 unicast
• B. IPv6 unicast
• C. VPNv4
• D. IPv4 unicast and IPv6 unicast
• E. IPv4 unicast and IPv6 unicast and VPNv4
• F. No address-family is enabled by default.

Answer: F

Explanation: http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.8/routing/command/reference/rr38bg p.pdf
An address family must be explicitly configured in the router configuration mode for the address family to be active in BGP. Similarly, an address family must be configured under the neighbor for the BGP session to be established for that address family. An address family must be configured in router configuration mode before it can be configured under a neighbor.

NEW QUESTION 2
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 3
Which option is a tool that is used to ensure that BGP AS does not become a transit AS?

• A. as-path filter-list
• B. local-preference
• C. ttl-security
• D. confederations

Answer: A

NEW QUESTION 4
Which four statements are correct regarding IS-IS operations? (Choose four.)

• A. By default, Level 1 routers within an IS-IS area do not carry any routing information external to the area to which they belon
• B. They use a default route to exit the area.
• C. Summarization should be configured on the Level 2 routers, which injects the Level 2 routes into Level 1.
• D. IS-IS supports "route leaking" in which selected Level 2 routes can be advertised by a Level 1/Level 2 router into Level 1.
• E. The IS-IS backbone is a contiguous collection of Level 1 capable routers, each of which can be in a different area.
• F. With IS-IS, an individual router is in only one area, and the border between areas is on the link that connects two routers that are in different areas.
• G. Cisco IOS XR Software supports multitopology for IPv6 IS-IS unless single topology is explicitly configured in IPv6 address-family configuration mode.

Answer: ACEF

Explanation: http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.0/routing/configuration/guide/rc3isis.html#wp1148617
Single-Topology IPv6 Support
Single-topology IPv6 support on Cisco IOS XR software allows IS-IS for IPv6 to be configured on interfaces along with an IPv4 network protocol. All interfaces must be configured with the identical set of network protocols and all routers in the IS-IS area (for Level 1 routing) or the domain (for Level 2 routing) must support the identical set of network layer protocols on all interfaces.
When single-topology support for IPv6 is used, only narrow link metrics, also known as old- style type, length, value (TLV) arguments, may be employed. During single-topology operation, one shortest path first (SPF) computation per level is used to compute both IPv4 and IPv6 routes. Using a single SPF is possible because both IPv4 IS-IS and IPv6 IS-IS routing protocols share a common link topology.
Because multitopology is the default behavior in the software, you must explicitly configure IPv6 to use the same topology as IPv4 in order to enable single-topology IPv6. Configure the single-topology command in ipv6 address family configuration submode of the IS-IS router stanza.
Multitopology IPv6 Support
Multitopology IPv6 support on Cisco IOS XR software differs from Cisco IOS software in that IS-IS assumes that multitopology support is required as soon as it detects interfaces configured for both IPv6 and IPv4 within the IS-IS stanza.
You must use the metric-style wide command to configure IS-IS to wide link metrics as multitopology link advertisements.

NEW QUESTION 5
Refer to the exhibit.

Which Cisco IOS XE command should be added to this configuration for the BFD protocol to operate successfully?

• A. Router1(config-if)#bfd echoRouter2(config-if)#bfd echo
• B. Router1(config-ospf-ar-if)#bfd fast-detectRouter2(config-ospf-ar-if)#bfd fast-detect
• C. Router1(config-router)#bfd all-interfacesRouter2(config-router)#bfd all-interfaces
• D. Router1(config- bfd)#echo-enableRouter2(config- bfd)#echo-enable

Answer: C

NEW QUESTION 6
Which option is a mechanism that can be implemented between two eBGP peers to communicate the routes each peer needs from the other?

• A. ORF
• B. ACL
• C. prefix list
• D. route map

Answer: A

NEW QUESTION 7
An EIGRP domain is redistributed into an OSPF NSSA area. On which router would this redistribution occur?

• A. stub border router
• B. summary router
• C. autonomous system boundary router
• D. backbone router

Answer: C

NEW QUESTION 8
Under which two conditions does an enterprise require BGP peering with its upstream Internet provider? (Choose two.)

• A. The enterprise has two exit points that are geographically separated and routing must be controlled so that delay variations are reduced.
• B. The enterprise has one exit point and must announce the IP class it has been assigned from its ISP.
• C. The enterprise has two Layer 2 links to the upstream ISP in the same location and wants to achieve redundancy.
• D. The enterprise needs a simple and efficient way to ensure proper routing for its AP subnets on its single ISP link.
• E. The enterprise is multihomed to two ISPs and has its own IP space AS number.

Answer: AE

NEW QUESTION 9
When using the show bgp ipv6 unicast summary command to verify the IPv6 BGP session status with the IPv6 BGP peers, you noticed the "St/PfxRcd" status for one of the IPv6 BGP peers is in the "Active" state. What does the "Active" state indicate?

• A. The IPv6 BGP session has been established with the IPv6 BGP peer.
• B. The router is in the process of sending BGP routing updates to the IPv6 BGP peer.
• C. The router is in the process of establishing the IPv6 BGP session with the IPv6 BGP peer.
• D. The router is exchanging BGP notification messages with its IPv6 BGP peer.

Answer: C

NEW QUESTION 10
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 11
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 12
What is the configured IS-IS circuit-type between the CE5 and PE5 routers and between the PE5 and PE6 routers? (Choose two.)

• A. Circuittype L1 between CE5 and PE5 4
• B. Circuittype L1/L2 between CE5 and PE5
• C. Circuittype L2 between CE5 and PE5
• D. Circuittype L1 between PE5 and PE6
• E. Circuittype L1/L2 between PE5 and PE6
• F. Circuittype L2 between PE5 and PE6

Answer: AF

Explanation: #show clns neighbor

NEW QUESTION 13
Refer to the exhibit.

A network engineer is asked to verify a multiarea IP IS-IS configuration before implementing it. Which statement is true?

• A. IS-type Level 1 must be configured on router B.
• B. Area addresses should be common.
• C. Wide metrics should be used only for router A.
• D. The system ID should be unique.

Answer: B

NEW QUESTION 14
Refer to the route policies exhibit.

Which five route policies will cause the routes to be dropped or passed? (Choose five)

• A. route-policy one will cause the routes to be dropped.
• B. route-policy two will cause the routes to be dropped.
• C. route-policy three will cause the routes to be dropped.
• D. route-policy four will cause the routes to be dropped.
• E. route-policy five will cause the routes to be dropped.
• F. route-policy one will cause the routes to be passed.
• G. route-policy two will cause the routes to be passed.
• H. route-policy three will cause the routes to be passed.
• I. route-policy four will cause the routes to be passed.
• J. route-policy five will cause the routes to be passed.

Answer: ACEGI

NEW QUESTION 15
Refer to the exhibit.

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

• A. route-policy INBOUND if destination in FILTER then pass endifrouter bgp 100 neighbor10.10.14.1 address-family ipv4 unicastroute-policy INBOUND in
• B. router bgp 100neighbor 10.10.14.1 address-family ipv4 unicastroute-policy FILTER in
• C. router bgp 100neighbor 10.10.14.1 address-family ipv4 unicastroute-policy SUBNETS in
• D. route-policy INBOUNDif destination in SUBNETS thenpass endifrouter bgp 100 neighbor 10.10.14.1 address-family ipv4 unicastroute-policy INBOUND in

Answer: A

NEW QUESTION 16
Refer to the exhibit.

Which configuration is correct for RX4 for an e-BGP session with R1?

• A. router bgp 100address-family ipv4 unicast!neighbor 10.10.14.1remote-as 10address- family ipv4unicastroute-policy POLICY in
• B. router bgp 100address-family ipv4 unicast!neighbor 10.10.14.1remote-as 100
• C. router bgp 100!neighbor 10.10.14.1remote-as 100
• D. router bgp 100!neighbor 10.10.14.1remote-as 10address-family ipv4 unicast

Answer: A

NEW QUESTION 17
Which two mandatory tasks must an IS-IS NSF-capable router perform for RP switchover? (Choose two.)

• A. Relearn the available IS-IS neighbors.
• B. Reacquire the contents of the LSD.
• C. Reset peering with the available IS-IS neighbors.
• D. Keep the existing contents of the LSD.
• E. Rediscover DIS for each link segment.

Answer: AB