[Free] Download New Updated (December) Cisco 642-889 Exam Questions 61-70

By | December 4, 2015

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QUESTION 61

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

 

Correct Answer: C

Ex
planation:

8 * (8-1) /2

 

 

QUESTION 62

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

 

Correct Answer: B

Explanation:

 clip_image002

 

http://etutorials.org/Networking/MPLS+VPN+Architectures/Part+2+MPLSbased+Virtual+Pri vate+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 fullesh 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.

 

 

QUESTION 63

Which VPN technology uses the Group Domain of Interpretation as the keying protocol and IPsec for encryption that is often deployed over a private MPLS core network?

 

A.

DMVPN

B.

GET VPN

C.

SSL VPN

D.

L2TPv3

 

Correct Answer: B

Explanation:

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6635/ps7180/deployment_guide_c07_554713.html

 

 

QUESTION 64

When using the Cisco EVC software infrastructure, a double-tagged frame with a customer VLAN of 10 and a service provider VLAN of 150 will be best matched by which encapsulation configuration?

 

A.

encapsulation dot1q 10 second-dot1q any

B.

encapsulation dot1q 10 second-dot1q 150

C.

encapsulation dot1q 10 second-dot1q 50-200

D.

encapsulation dot1q 10

E.

encapsulation dot1q 150

 

Correct Answer: E

 

 

QUESTION 65

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

 

Correct Answer: A

 

 

QUESTION 66

Which option is used as a loop prevention mechanism to support MPLS VPN customers with multihomed sites?

 

A.

BGP down bit

B.

sham links

C.

AS override

D.

SOO extended BGP community

E.

allow as-in

 

Correct Answer: D

Explanation:

http://www.cisco.com/en/US/docs/ios/12_4t/12_4t11/htbgpsoo.html

 

Site of Origin BGP Community Attribute

The site-of-origin (SoO) extended community is a BGP extended community attribute that is used to identify routes that have originated from a site so that the readvertisement of that prefix back to the source site can be prevented. The SoO extended community uniquely identifies the site from which a router has learned a route. BGP can use the SoO value associated with a route to prevent routing loops.

 

 

QUESTION 67

A customer needs Internet and MPLS services from the service provider and needs to ensure traffic from the Internet network does not constrain MPLS traffic. Which shared MPLS/Internet service type best accommodates this requirement?

 

A.

partial separation

B.

full separation

C.

Multisite Internet Access

D.

Internet tunnel over MPLS

 

Correct Answer: B

 

 

QUESTION 68

In hierarchical VPLS implementations, which two access architectures can be used between the UPE and NPE? (Choose two.)

 

A.

EoMPLS

B.

MP-BGP

C.

Frame Relay

D.

802.1ad

 

Correct Answer: AD

Explanation:

http://www.cisco.com/en/US/docs/switches/metro/me3600x_3800x/software/release/12.2_52_ey/configuration/guide/swmpls.html#wp1244272

 

H-VPLS uses spoke connections, usually between Layer 2 switches acting as the CE and PE devices at the service provider’s point-of presence (POP). The spoke connections can be either an IEEE 802.1Q tagged connection or an MPLS LSP.

 

 

QUESTION 69

Refer to the exhibit. PE1 and PE2 are advertising the same subnet 10.10.10.0/24 to PE3. Which PE advertised subnet is installed at the PE3 XYZ BGP table?

 

clip_image004

 

A.

PE2 subnetbecause it has the same RD value as PE3

B.

PE2 subnet because it has the same export RT value as export RT on PE3

C.

PE1 subnetbecause it has the same RD value as PE3

D.

PE1 subnet because it has the same export RT value as import RT on PE3

 

Correct Answer: D

 

 

QUESTION 70

Which option represents an AToM pseudowire basic configuration in Cisco IOS XR device?

 

A.

pseudowire-class name_class

encapsulation mpls

!

B.

pseudowire-class name_class

encapsulation l2tpv3

!

C.

l2vpn pw-class name

encapsulation mpls

!

D.

l2vpn xconnect group group-name

p2p xconnect-name

E.

neighbor ip-address pw-id pseudowire-id

 

Correct Answer: C

 

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