Cisco 642-889 Braindump 2021

NEW QUESTION 1
Implementing H-VPLS instead of VPLS reduces which requirement?

• A. having a full mesh of PWs between all the PE routers in the service provider MPLS core
• B. having a full mesh of PWs between all the UPE routers
• C. having to implement QinQ tagging between the UPE and the NPE
• D. having to implement MPLS LDP between the UPE and the NPE
• E. the overhead of using BGP or LDP autodiscovery

Answer: A

Explanation:

NEW QUESTION 2
When is it appropriate to activate the VPNv6 address family?

• A. when implementing 6PE
• B. when running dual stack at the provider edge
• C. when implementing 6to4 tunneling
• D. when implementing 6VPE

Answer: D

NEW QUESTION 3
When implementing Layer 3 MPLS VPNs on Cisco IOS/IOS XE PE routers, which PE-to-CE routing protocol requires a separate routing process to be created for each VRF?

• A. EIGRP
• B. RIPv2
• C. OSPF
• D. BGP

Answer: C

NEW QUESTION 4
Refer to the exhibit.

Given the output shown, which two statements are true? {Choose two.}

• A. The configured remote AS for neighbor 10.1.1.1 is 1234.
• B. Both prefixes that are referenced by network commands will be visible with the show bgp command from the information that is shown in the output.
• C. The neighbor 10.1.1.1 cannot learn any routes from this router.
• D. The router cannot learn any routes for neighbor 10.1.1.1.
• E. Routes from the Internet VRF that are injected into BGP through redistribution will be advertised to neighbor 10.1.1.1.

Answer: AC

NEW QUESTION 5
A customer is connecting to a Cisco IOS XR PE device via BGP. The peering session is up and the customer is advertising routes, but the provider is not receiving any. Which issue is the most likely cause?

• A. The IOS XR device drops inbound routing updates on eBGP peers without an inbound route-policy.
• B. The IOS XR device requires as-override on all eBGP customer peers.
• C. The IOS XR device requires labeled-unicast peering sessions to eBGP customers.
• D. The IOS XR device drops inbound routing updates on eBGP peers that do not send extended communities.

Answer: A

NEW QUESTION 6
When implementing a Layer 2 transport subinterface on a Cisco IOS XR router, which encapsulation option is used to match any packets that are not matched by any other service instances?

• A. default
• B. untagged
• C. any
• D. tag

Answer: A

Explanation:

NEW QUESTION 7
Which two methods can be used for VPLS PW signaling? {Choose two.}

• A. static
• B. BGP
• C. IGP
• D. LDP
• E. RSVP

Answer: BD

Explanation:

NEW QUESTION 8
Which three Layer 3 VPN technologies are based on the overlay model? {Choose three.}

• A. ATM virtual circuits
• B. Frame Relay virtual circuits
• C. GRE/IPsec
• D. L2TPv3
• E. MPLS Layer 3 VPNs
• F. DMVPNs

Answer: CDF

Explanation:
The overlay model, where the service provider provides emulated leased lines to the customer.
The service provider provides the customer with a set of emulated leased lines. These leased lines are called VCs, which can be either constantly available {PVCs} or established on demand {SVCs}. The QoS guarantees in the overlay VPN model usually are expressed in terms of bandwidth guaranteed on a certain VC {Committed Information Rate or CIR} and maximum bandwidth available on a certain VC {Peak Information Rate or PIR}. The committed bandwidth guarantee usually is provided through the statistical nature of the Layer 2 service but depends on the overbooking strategy of the service provider The peer-to-peer model, where the service provider and the customer exchange Layer 3 routing information and the provider relays the data between the customer sites on the optimum path between the sites and without the customer's involvement.
The peer-to-peer VPN model was introduced a few years ago to alleviate the drawbacks of the overlay VPN model. In the peer-to-peer model, the Provider Edge {PE} device is a router {PE-router} that directly exchanges routing information with the CPE router. The Managed Network service offered by many service providers, where the service provider also manages the CPE devices, is not relevant to this discussion because it's only a repackaging of another service. The Managed Network provider concurrently assumes the role of the VPN service provider providing the VPN infrastructure} and part of the VPN customer role {managing the CPE device}.
The peer-to-peer model provides a number of advantages over the traditional overlay model:
Routing {from the customer's perspective} becomes exceedingly simple, as the customer router exchanges routing information with only one {or a few} PE-router, whereas in the overlay VPN network, the number of neighbor routers can grow to a large number.
Routing between the customer sites is always optimal, as the provider routers know the customer's network topology and can thus establish optimum inter-site routing.
Bandwidth provisioning is simpler because the customer has to specify only the inbound and outbound bandwidths for each site {Committed Access Rate [CAR] and Committed Delivery Rate [CDR]} and not the exact site-to-site traffic profile.
The addition of a new site is simpler because the service provider provisions only an additional site and changes the configuration on the attached PE-router. Under the overlay VPN model, the service provider must provision a whole set of VCs leading from that site to other sites of the customer VPN.
Prior to an MPLS-based VPN implementation, two implementation options existed for the peer-to-peer VPN model: The shared-router approach, where several VPN customers share the same PE-router.
The dedicated-router approach, where each VPN customer has dedicated PE-routers.

NEW QUESTION 9
Which option is the minimal configuration required inside the L2VPN section of a Cisco IOS XR PE router to activate VPLS functionality?

• A. l2vpnbridge group test bridge-domain testinterface TenGigE0/0/0/1.30!vfi testvpn-id 600 autodiscovery bgp rd 10.10.10.1:30route-target 1:300 signaling-protocol bgp ve-id 10
• B. l2vpnbridge group test bridge-domain testinterface TenGigE0/0/0/1.30!vfi testneighbor 10.10.10.2 pw-id 1400mpls static label local 1400 remote 1500
• C. l2vpnbridge group test bridge-domain testinterface TenGigE0/0/0/1.30!vfi testneighbor 10.10.10.2 pw-id 1400
• D. l2vpnbridge group test bridge-domain testinterface TenGigE0/0/0/1.30!vfi testvpn-id 600 autodiscovery bgp rd 10.10.10.1:30route-target 1:300 signaling-protocol bgp
• E. l2vpnbridge group test bridge-domain test vfi test autodiscovery bgp rd 10.10.10.1:30route-target 1:300 signaling-protocol bgp ve-id 10

Answer: C

NEW QUESTION 10
When verifying Layer 3 MPLS VPN operations, which Cisco IOS XR show command is best used to verify that the PE router is receiving the routes from the CE router?

• A. show route
• B. show route vrf vrf-name
• C. show bgp vpnv4 vrf vrf-name
• D. show bgp vpnv4 unicast ip-prefix

Answer: B

Explanation:
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.7/routing/configuration/guide/rc37rib.html

NEW QUESTION 11
When implementing nonhierarchical VPLS with eight PE routers, how many total PWs will be required between the PE routers?

• A. 8
• B. 16
• C. 28
• D. 32
• E. 64

Answer: C

Explanation:
8* {8-1} /2

NEW QUESTION 12
What is the purpose of the route distinguisher in a service provider network?

• A. to identify which prefixes should be imported
• B. to identify customer local prefixes
• C. to identify customer global prefixes
• D. to identify which prefixes should be exported from BGP

Answer: C

NEW QUESTION 13
What are the two AToM interworking modes? {Choose two.}

• A. bridged {interworking ethernet}
• B. routed {interworking ip}
• C. label-switched {interworking mpls}
• D. transparent {interworking transparent}

Answer: AB

Explanation:
http://www.cisco.com/en/US/docs/ios/ios_xe/mpls/configuration/guide/mp_l2vpn_intrntwkg_xe.html
Interworking is a transforming function that is required to interconnect two heterogeneous attachment circuits {ACs}. Several types of interworking functions exist. The function that is used would depend on the type of ACs being used, the type of data being carried, and the level of functionality required. The two main Layer 2 Virtual Private Network {L2VPN} interworking functions supported in Cisco IOS XE software are bridged and routed interworking.
Layer 2 {L2} transport over multiprotocol label switching {MPLS} and IP already exists for like-to-like ACs, such as Ethernet-to-Ethernet or Point-to-Point Protocol {PPP}-to-PPP. L2VPN Interworking builds on this functionality by allowing disparate ACs to be connected. An interworking function facilitates the translation between different L2 encapsulations.

NEW QUESTION 14
Which two statements about implementing a separate MPLS VPN to provide customers Internet access are correct? {Choose two.}

• A. The Internet gateway router will act as a CE router.
• B. Customers will use separate interfaces for VPN and Internet access.
• C. Customers are assigned to the Internet VPN.
• D. Internet routes will be leaked from the PE global routing table to the customer VRF.

Answer: AC

NEW QUESTION 15
When implementing VPLS on Cisco IOS XR routers, the customer-facing subinterfaces on the PE routers are assigned to which Cisco EVC component?

• A. bridge group
• B. bridge domain
• C. VFI
• D. Layer 2 transport
• E. BVI

Answer: B

Explanation:

NEW QUESTION 16
Which option is a valid Cisco IOS XR BGP Layer 3 IPv4 MPLS VPN configuration?

• A. router bgp 65001no bgp default ipv4-unicast bgp log-neighbor-changesneighbor 1.2.3.4 remote-as 65001 neighbor 1.2.3.4 update-source Loopback0 address-family vpnv4neighbor 1.2.3.4 activateneighbor 1.2.3.4 send-community extended exit-address-familyaddress-family ipv4 vrf VPN redistribute ospf 100
• B. router bgp 65001no bgp default ipv4-unicast bgp log-neighbor-changesneighbor 1.2.3.4 remote-as 65001 neighbor 1.2.3.4 update-source Loopback0 address-family vpnv4neighbor 1.2.3.4 activate exit-address-familyaddress-family ipv4 vrf VPN redistribute ospf 100
• C. router bgp 100address-family vpnv4 unicast neighbor 2.2.2.2remote-as 100update-source Loopback0 address-family vpnv4 unicast!vrf VPN_A rd 100:1address-family ipv4 unicast redistribute ospf 100
• D. router bgp 100address-family vpnv4 unicast neighbor 2.2.2.2remote-as 100update-source Loopback0 address-family ipv4 unicast!vrf VPN_A rd 100:1address-family ipv4 unicast redistribute ospf 100

Answer: C

NEW QUESTION 17
When implementing CSC services, which two methods can be used to exchange label information between the downstream CSC customer carrier and the CSC backbone carrier? {Choose two.}

• A. using MP-BGP
• B. using RSVP
• C. using IGP and LDP
• D. using back-to-back VRF
• E. using front VRF and internal VRF

Answer: AC

Explanation:
http://www.cisco.com/en/US/docs/net_mgmt/ip_solution_center/4.0/mpls/user/guide/9_iscqsg.html
Since the CSC-PE routers do not have to carry external routes in the VRF routing table, they can use the incoming label in the packet to forward the customer carrier Internet traffic. Adding MPLS to the routers provides a consistent method of transporting packets from the customer carrier to the backbone carrier. MPLS allows the exchange of an MPLS label between the CSC-PE and the CSC-CE routers for every internal customer carrier route. The routers in the customer carrier have all the external routes either through IBGP or route redistribution to provide Internet connectivity.
When a backbone carrier and the customer carrier both provide BGP/MPLS VPN services, the method of transporting data is different from when a customer carrier provides only ISP services. The following list highlights those differences.
•When a customer carrier provides BGP/MPLS VPN services, its external routes are VPN-IPv4 routes. When a customer carrier is an ISP, its external routes are IP routes.
•When a customer carrier provides BGP/MPLS VPN services, every site within the customer carrier must use MPLS. When a customer carrier is an ISP, the sites do not need to use MPLS.

NEW QUESTION 18
Which type of VPN requires a full mesh of virtual circuits to provide optimal site-to-site connectivity?

• A. MPLS Layer 3 VPNs
• B. Layer 2 overlay VPNs
• C. GET VPNs
• D. peer-to-peer VPNs

Answer: B

Explanation:

http://etutorials.org/Networking/MPLS+VPN+Architectures/Part+2+MPLSbased+Virtual+Private+Networks/Chapter+7.+Virtual+Private+Network+VPN+Implementation+Options/Overlay+and+Peer-to-peer+VPN+Model/
Two VPN implementation models have gained widespread use:
The overlay model, where the service provider provides emulated leased lines to the customer.
The service provider provides the customer with a set of emulated leased lines. These leased lines are called VCs, which can be either constantly available {PVCs} or established on demand {SVCs}. The QoS guarantees in the overlay VPN model usually are expressed in terms of bandwidth guaranteed on a certain VC {Committed Information Rate or CIR} and maximum bandwidth available on a certain VC {Peak Information Rate or PIR}. The committed bandwidth guarantee usually is provided through the statistical nature of the Layer 2 service but depends on the overbooking strategy of the service provider The peer-to-peer model, where the service provider and the customer exchange Layer 3 routing information and the provider relays the data between the customer sites on the optimum path between the sites and without the customer's involvement. The peer-to-peer VPN model was introduced a few years ago to alleviate the drawbacks of the overlay VPN model. In the peer-to-peer model, the Provider Edge {PE} device is a router {PE-router} that directly exchanges routing information with the CPE router. The Managed Network service offered by many service providers, where the service provider also manages the CPE devices, is not relevant to this discussion because it's only a repackaging of another service. The Managed Network provider concurrently assumes the role of the VPN service provider {providing the VPN infrastructure} and part of the VPN customer role {managing the CPE device}. The peer-to-peer model provides a number of advantages over the traditional overlay model:
Routing {from the customer's perspective} becomes exceedingly simple, as the customer router exchanges routing information with only one {or a few} PE-router, whereas in the overlay VPN network, the number of neighbor routers can grow to a large number.
Routing between the customer sites is always optimal, as the provider routers know the customer's network topology and can thus establish optimum inter-site routing.
Bandwidth provisioning is simpler because the customer has to specify only the inbound and outbound bandwidths for each site {Committed Access Rate [CAR] and Committed Delivery Rate [CDR]} and not the exact site-to-site traffic profile.
The addition of a new site is simpler because the service provider provisions only an additional site and changes the configuration on the attached PE-router. Under the overlay VPN model, the service provider must provision a whole set of VCs leading from that site to other sites of the customer VPN.
Prior to an MPLS-based VPN implementation, two implementation options existed for the peer-to-peer VPN model: The shared-router approach, where several VPN customers share the same PE-router.
The dedicated-router approach, where each VPN customer has dedicated PE-routers.
Overlay VPN paradigm has a number of drawbacks, most significant of them being the need for the customer to establish point-to-point links or virtual circuits between sites. The formula to calculate how many point-to-point links or virtual circuits you need in the worst case is {{n}{n-1}}/2, where n is the number of sites you need to connect. For example, if you need to have full-mesh connectivity between 4 sites, you will need a total of 6 point-to-point links or virtual circuits. To overcome this drawback and provide the customer with optimum data transport across the Service Provider backbone, the peer-to-peer VPN concept was introduced where the Service Provider actively participates in the customer routing, accepting customer routes, transporting them across the Service Provider backbone and finally propagating them to other customer sites.

NEW QUESTION 19
What is the primary difference between 6PE and 6VPE?

• A. 6VPE does not require an MPLS core.
• B. 6VPE requires an IPv6-aware core.
• C. 6VPE provides IPv6 VPN services.
• D. 6VPE tunnels IPv6 packets inside IPv4 packets.

Answer: C

Explanation:
6PE is for transporting ipv6 natively and 6VPE is for ipv6 mpls vpns

NEW QUESTION 20
What is an advantage of using the Cisco EVC infrastructure to implement carrier-class Ethernet services that are not available on non-EVC-capable platforms?

• A. PW redundancy
• B. interworking support
• C. PW stitching support
• D. flexible frame-matching support and VLAN tag manipulation
• E. local cross-connect support

Answer: D

Explanation:
http://www.cisco.com/web/YU/events/expo_08/pdfs/Carrier_Ethernet_Marek_Moskal.pdf

NEW QUESTION 21
A network engineer is tasked to implement an AToM VPN for a given customer to emulate a Frame Relay virtual circuit over the MPLS-enabled core network. Which command enables Frame Relay to forward frames from the attachment circuit over the emulated session in regular Cisco IOS Software?

• A. ip route 0.0.0.0 0.0.0.0 tailend_router_ip
• B. encapsulation frame-relay
• C. frame-relay switching
• D. frame-relay intf-type dce

Answer: C

NEW QUESTION 22
In which configuration mode is a route distinguisher configured in a Cisco IOS XR router?

• A. config-vrf
• B. config-vrf-af
• C. config-bgp
• D. config-bgp-af
• E. config-bgp-vrf

Answer: E

Explanation:
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.6/routing/configuration/guide/rc36book.pdf

NEW QUESTION 23
Which two MPLS QoS models described by RFC3270 are used for CE-PE QoS implementation? {Choose two.}

• A. best effort
• B. pipe
• C. uniform
• D. integrated services
• E. differentiated services

Answer: BC

NEW QUESTION 24
With Layer 3 MPLS VPN implementations on Cisco IOS XR PE routers, an interface is assigned to a VRF using the vrf command in which configuration mode?

• A. RP/0/RP0/CPU0:PE{config-vrf}#
• B. RP/0/RP0/CPU0:PE{config-if}#
• C. RP/0/RP0/CPU0:PE{config-bgp}#
• D. RP/0/RP0/CPU0:PE{config-bgp-af}#

Answer: B

Explanation:

NEW QUESTION 25
Refer the exhibit.




On PE7, how many multiprotocol IBGP routes are learned from PE8 and what is the next-hop IP address? {Choose two.}

• A. 1
• B. 2
• C. 3
• D. 10.8.1.1
• E. 172.16.8.1
• F. 192.168.108.81

Answer: BE

Explanation:
Show ip bgp vpnv4 all --- i tag field is the answer

NEW QUESTION 26
......