Implementing Cisco Service Provider Next-Generation Edge Network Services

Exam Number 642-889 SPEDGE  

Associated Certifications CCNP Service Provider 

Duration 90 minutes (65 - 75 questions) 

Available Languages English 

Register Pearson VUE 

Exam Policies Read current policies and requirements 

Exam Tutorial Review type of exam questions 

 

The 642-889 SPEDGE Implementing Cisco Service Provider Next-Generation Edge Network Services tests a candidate's knowledge of service provider VPN solutions through enabling point of presence to provide Layer 2 and Layer 3 VPNs. This exam covers the Cisco IOS, IOS XE and IOS XR operating systems. Candidates can prepare for this exam by taking the Implementing Cisco Service Provider Next-Generation Edge Network Services (SPEDGE) course.

 

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NO.1 Which Layer 2 protocol parameters can be carried inside the control word when implementing

AToM service?

A. PW ID

B. Frame Relay FECN, BECN, and DE bits

C. encapsulation type

D. VC type

Answer: B

Explanation:

http://www.cisco.com/en/US/products/ps6603/products_qanda_item09186a008009d4e3.sh

tml#wp39173

Q. How does Frame Relay over MPLS work?

A. Traffic is encapsulated in MPLS packets and forwarded across the MPLS network. When

encapsulating Frame Relay over MPLS, the Frame Relay header and the frame check sequence (FCS)

are stripped from the packet. The bits for Backward Explicit Congestion Notification (BECN), Forward

Explicit Congestion Notification (FECN), Discard Eligibility (DE) and Command/Response (C/R) are

carried across the MPLS network in the "Control Word" header.

 

NO.2 A presale engineer is asked to advise about the various MPLS VPN designs to best fit the

customer requirements. Which two MPLS L2VPN features should be highlighted as advantages over a

MPLS L3VPN? (Choose two.)

A. An MPLS L2VPN design is a more appropriate solution for disaster recovery and data backup.

B. An MPLS L2VPN is a more redundant design compared to a MPLS L3VPN solution.

C. An MPLS L2VPN design does not require routing interaction with the service provider network.

D. An MPLS L2VPN design virtually extends the broadcast domain boundary allowing for the

customer IGP to fully interoperate between remote sites.

E. An MPLS L2VPN design does not require monitoring, which provides a significant cost-saving

solution.

Answer: C,D

 

NO.3 Which protocol is used to hide customer VLANs inside the provider backbone network?

A. 802.1ap

B. 802.1x

C. 802.1ad

D. 802.1q

Answer: C

 

NO.4 A customer is connecting toa 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 devicerequires as-override on all eBGP customer peers.

C. The IOS XR devicerequires labeled-unicast peering sessions to eBGP customers.

D. The IOS XR devicedrops inbound routing updates on eBGP peers that do not send extended

communities.

Answer: A

 

NO.5 Which method is used to provide inter-AS AToM services?

A. back-to-back VRF

B. targeted LDP

C. pseudowire stitching

D. AToM interworking

E. Cisco MPLS TE tunnels

F. autodiscovery

Answer: C

Explanation:

http://www.cisco.com/en/US/docs/optical/cpt/r9_3/configuration/guide/cpt93_configuration_

chapter_0111.html

 

NO.6 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+Pri

vate+Networks/Chapter+7.+Virtual+Private+Network+VPN+Implementation+Options/Overl

ay+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-topoint 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.

 

NO.7 Which technology does an N-PE most likely use to pass traffic to the U-PE that is destined for

the access switch?

A. pseudowire

B. MPLS TE

C. OSPF

D. IS-IS

Answer: A

 

NO.8 An engineer is configuring VPLS BGP-based autodiscovery on a Cisco IOS XE PE router. Which

two configurations must be included for proper implementation? (Choose two.)

A. router bgp 61000 neighbor 172.16.10.2 remote-as 61000

B. router bgp 61000 address-family l2vpn vpls send-community extended

C. router bgp 61000 neighbor 172.16.10.2 remote-as 62000

D. router bgp 61000 address-family l2vpn vpls send-community-eBGP

E. l2vpn vfi context vpls1 autodiscovery bgp signaling ldp router bgp 61000 neighbor 172.16.10.2

remote-as 62000

F. l2vpn vfi context vpls1 autodiscovery bgp signaling ldp router bgp 61000 neighbor 172.16.10.2

remote-as 61000

Answer: A,B