Download New Latest (May) Cisco 642-889 Actual Tests 1-10

By | May 17, 2015

Ensurepass

Exam A

 

QUESTION 1

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:

clip_image001

 

C:Documents and Settingsuser-nwzDesktop1.JPG

 

 

QUESTION 2

When implementing MPLS Layer 3 VPNs with customers running OSPF as the CE-PE routing protocol, the service provider MPLS backbone looks like what to the CE routers?

 

A.

the backbone (Area 0)

B.

an external routing domain

C.

a superbackbone that is transparent to the CE OSPF routers

D.

a transit area (similar to a transit area for supporting virtual links)

 

Answer: C

 

 

QUESTION 3

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.

&n

bsp;

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.

 

 

QUESTION 4

clip_image002

 

 

 

clip_image003

 

clip_image004

 

Which statement is correct regarding the pseudowire on connects PE7 to the 10.8.1.1 neighbor?

 

A.

The control word is enabled on both ends of the pseudowire

B.

The MTU size is 1500 bytes on both ends of the pseudowire

C.

Pseudowire backup is enabled

D.

The pseudowire is in the down state

 

Answer: B

Explanation:show xconnect all

 

 

 

show ip interface brief

show mpls l2transport vc

show cable l2-vpn xconnect mpls-vc-map

 

 

QUESTION 5

Which flavor of MPLS Layer 3 VPN has MPLS enabled on PE-CE links?

 

A.

basic

B.

CSC

C.

inter-AS

D.

AToM

E.

VPLS

 

Answer: B

Explanation:http://www.cisco.com/en/US/docs/ios/12_0st/12_0st14/feature/guide/csc.html

 

 

 

clip_image005

 

C:Documents and Settingsuser-nwzDesktop1.JPG

 

 

QUESTION 6

Which two Layer 2 VPN methods support interworking between customer sites with different Layer 2 encapsulation at each end (for example, Frame Relay to Ethernet interworking)? (Choose two.)

 

A.

AToM

B.

VPLS

C.

GET VPN

D.

L2TPv3

 

Answer: AD

Explanation:http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gtl2tpv3.html#wp1040784

 

The Layer 2 Tunnel Protocol Version 3 feature expands on Cisco support of the Layer 2 Tunnel Protocol Version 3 (L2TPv3). L2TPv3 is an Internet Engineering Task Force (IETF) l2tpext working group draft that provides several enhancements to L2TP for the capability to tunnel any Layer 2 payload over L2TP.

 

Specifically, L2TPv3 defines the L2TP protocol for tunneling Layer 2 payloads over an IP core network using Layer 2 virtual private networks (VPNs). Benefits of this feature include the following:

·L2TPv3 simplifies deployment of VPNs

·L2TPv3 does not require Multiprotocol Label Switching ·L2TPv3 supports Layer 2 tunneling over IP for any payload http://www.cisco.com/en/US/products/ps6646/products_ios_protocol_option_home.html Cisco Any Transport over MPLS (AToM) is a solution for transporting Layer 2 packets over an MPLS backbone. It enables Service Providers to supply connectivity between customer sites with existing data link layer (Layer 2) networks via a single, integrated, packet-based network infrastructure: a Cisco MPLS network. Without separate networks that each have network management environments, Service Providers can deliver Layer 2 connections over an MPLS backbone.

 

Cisco AToM provides a common framework to encapsulate and transport supported Layer 2 traffic types over an MPLS network core. Service Providers can use a single MPLS network infrastructure to offer connectivity for supported Layer 2 traffic and for IP traffic in Layer 3 VPNs.

 

 

QUESTION 7

In Layer 3 MPLS VPN implementations, if a customer is using the same AS number at both customer sites and the PE-to-CE routing protocol is BGP, what must
be enabled on the PE router?

 

A.

BGP AS override

B.

BGP allowas-in

C.

BGP SOO extended community

D.

BGP AS path prepending

 

Answer: A

Explanation:https://supportforums.cisco.com/docs/DOC-21837

Loop prevention in BGP is done by verifying the AS number in the AS Path. If the receiving router sees its own AS number in the AS Path of the received BGP packet, the packet is dropped. The receiving Router assumes that the packet was originated from its own AS and has reached the same place from where it originated initially.

 

The feature could be a disaster if customers are using same AS number along the various sites and disallows customer sites having identical AS numbers to be linked by another AS number. In such a scenario, routing updates from one site will be dropped when the other site receives them.

To override this feature, AS-Override function causes to replace the AS number of originating router with the AS number of the sending BGP router. The command is neighbor ip-address as-override and can only be executed under the VPNv4 address- family

 

 

QUESTION 8

When implementing MPLS Layer 3 VPN services, which CE-PE routing method does not require the use of the redistribute command to enable the customer routes to be advertised through the MPLS cloud between the customer sites?

 

A.

EIGRP

B.

OSPF

C.

IS-IS

D.

BGP

E.

static routing

F.

OSPF or IS-IS

 

Answer: D

 

 

QUESTION 9

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

 

clip_image006

 

C:Documents and Settingsuser-nwzDesktop1.JPG

 

 

QUESTION 10

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

Free VCE & PDF File for Cisco 642-889 Real Exam

Instant Access to Free VCE Files: CCNA | CCNP | CCIE …
Instant Access to Free PDF Files: CCNA | CCNP | CCIE …