642-887 SPCORE Implementing Cisco Service Provider Next-Generation Core Network Services

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Exam Number 642-887 SPCORE
Associated Certifications CCNP Service Provider
Duration 90 minutes (65 – 75 questions)
Available Languages English
Register Pearson VUE

The 642-887 SPCORE Implementing Cisco Service Provider Next-Generation Core Network Services exam. This exam tests a candidate’s knowledge of the concepts and implementation of MPLS technology and MPLS-TE services. It also validates the understanding of technology principles of basic Quality of Service, and Quality of Service with Multi Protocol Label Switching (MPLS) to implement advanced features and functions. Candidates can prepare for this exam by taking the Implementing Cisco Service Provider Next-Generation Core Network Services (SPCORE) course.

The 642-887, SPCORE, Implementing Cisco Service Provider Next-Generation Core Network Services exam is associated with the CCNP® Service Provider certification. This 90-minute, 65−75 questions exam tests a candidate’s knowledge on the concepts and implementation of MPLS, LDP, MPLS-TE and QoS policies from the Service Provider perspective. 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 Core Network Services (SPCORE) course. The exam is closed book and no outside reference materials are allowed.

The following topics are general guidelines for the content likely to be included on the exam. However, other related topics may also appear on any specific delivery of the exam. In order to better reflect the contents of the exam and for clarity purposes, the guidelines below may change at any time without notice.

1.0 QOS in a Service Provider IP NGN Environment 38%

1.1 Describe the DiffServ and IntServ QoS models

1.2 Describe the QoS mechanisms (classification and marking, congestion management and avoidance, traffic policing and shaping)

1.3 Describe IPv6 Flow Label

1.4 Describe trust boundaries in enterprise and SP environments

1.5 Describe Cisco MQC for QoS configurations

1.6 Describe hierarchical QoS configurations

1.7 Describe the Cisco NBAR feature for discovering network protocols and for packets classifications

1.8 Describe the typical Edge PE routers and Core P routers QoS requirements

1.9 Implement classification and marking in an inter-domain network using QPPB on Cisco IOS-XR and IOS-XE

1.10 Implement class-based markings on Cisco IOS-XR and IOS-XE

1.11 Implement QoS pre-classify on tunnel interface on Cisco IOS-XR and IOS-XE

1.12 Implement CB-WFQ on Cisco IOS-XR and IOS-XE

1.13 Implement LLQ on Cisco IOS-XR and IOS-XE

1.14 Implement WRED on Cisco IOS-XR and IOS-XE

1.15 Implement traffic policing on Cisco IOS-XR and IOS-XE

1.16 Implement traffic shaping on Cisco IOS-XR and IOS-XE

1.17 Describe LPTS and hardware rate limiters on Cisco IOS-XR routers

1.18 Describe MPLS EXP bits

1.19 Describe MPLS QoS implementation concepts and models

1.20 Implement MPLS DiffServ tunneling on Cisco IOS-XR and IOS-XE

1.21 Troubleshoot QoS IOS-XR and IOS-XE configuration errors

2.0 MPLS/LDP in a Service Provider IP NGN Environment 32%

2.1 Describe the CEF, FIB, LFIB and LIB tables on Cisco routers

2.2 Describe MPLS labels and label stack operations on Cisco routers

2.3 Describe LDP operations in Cisco routers

2.4 Describe MPLS OAM (MPLS LSP ping and MPLS traceroute)

2.5 Describe MPLS applications in service provider environment

2.6 Implement LDP on Cisco IOS-XR and IOS-XE

2.7 Implement LDP high availability features on Cisco IOS-XR and IOS-XE

2.8 Troubleshoot LDP on IOS-XR and IOS-XE configuration errors

3.0 MPLS/LDP in a Service Provider IP NGN Environment 22%

3.1 Describe MPLS traffic engineering (TE) concepts

3.2 Describe MPLS TE constraint-based path computations

3.3 Describe the details of MPLS TE tunnels, including path setup procedures and path maintenance

3.4 Describe methods of assigning traffic into MPLS TE tunnels

3.5 Implement MPLS TE tunnels on Cisco IOS-XR and IOS-XE

3.6 Implement MPLS TE bandwidth control on Cisco IOS-XR and IOS-XE

3.7 Implement MPLS TE link and node protections on Cisco IOS-XR and IOS-XE

4.0 Transport Technologies 8%

4.1 Describe the SP core transition from ATM/SONET/SDH based backbone to

packet based IP/MPLS backbone

4.2 Implement 10/40/100 Gigabit Ethernet Interfaces on Cisco IOS-XR routers

4.3 Describe DWDM, IPoDWDM and ROADM

4.4 Implement IPoDWDM controller/interface on Cisco IOS-XR routers

QUESTION 1
What is the correct formula for determining the CIR?

A. CIR = Bc/Tc
B. CIR = Bc x Tc
C. CIR = Tc/Bc
D. CIR = Bc + Be
E. CIR = Tc/(Bc+Be)
F. CIR = (Bc+Be)/Tc

Answer: A

Explanation:
Committed Information Rate (CIR) – the rate the device will send at (on average) over a one
second period.
The default CIR when traffic-shaping is enabled on the interface is 56K. CIR is also referred to as
the “target rate”. Since the device is forced to send at the AR, it does not send all of the time
(within one second) Â in order to send an average amount of data that equals the CIR.
Minimum CIR (mincir) – the rate the service provider guarantees to accept. Theoretically, the
provider will set the DE bit for all traffic above this rate. Mincir is designed to be used in
conjunction with adaptive shaping. With adaptive shaping, the router will throttle down in the event
of congestion. The router will not throttle down below this value.
Committed Burst (Bc) – the number of committed bits allows to be sent during a given interval.
The device sends an average amount of traffic to achieve the CIR. The Bc value defaults to 1/8 of
the configured CIR for speeds below 650K. For speeds above that, it is roughly 1/16 of CIR.
Excess Burst (Be) – the number of non-committed bits the router is allowed to send above Bc
during the first interval (Tc). The amount of Be “credits” is derived from unused Bc credits in
previous intervals. There is no limit to how long Be can “store” unused Bc credits. It is a common
misconception that Be can only store credits from the previous interval or the previous second.
There is no default Be value.
Committed Rate Measurement Interval (Tc) – the time interval over whic Bc or Bc+Be can be
transmitted. The max value is 125 ms and the minimum value is 10 ms.
The Formula
CIR, Tc, and Bc are related mathematically by the following formula:
CIR = Bc/(Tc/1000) Notice the division of Tc by 1000 is used to convert milliseconds into seconds
– the common measurement of CIR and Bc.


QUESTION 2
DS-TE implementations on Cisco routers support which bandwidth pool(s) and class type(s)?
(Choose two.)

A. global pool only
B. subpool only
C. global pool and subpool
D. class-type 0 only
E. class-type 1 only
F. class-type 0 and class-type 1

Answer: C,F

Explanation:
Differential Service Tunnels
Differential Service Traffic Engineering (TE) is an extension of the regular MPLS Traffic
Engineering (MPLSTE) feature. Regular TE does not provide bandwidth guarantees to different
traffic classes. A single bandwidth pool (global pool) is used in regular TE that is shared by all
traffic. In order to support various class of service (CoS), the ability to provide multiple bandwidth
pools is required. These bandwidth pools then can be treated differently based on the requirement
for the traffic class using that pool.
In RSVP global and subpools reservable bandwidths are configured on a per interface basis to
accommodate TE tunnels on the node. Available bandwidth from all configured bandwidth pools is
advertised using Interior Gateway Protocol (IGP). RSVP is used to signal the TE tunnel with
appropriate bandwidth pool requirements.


QUESTION 3
Which field in the MPLS shim header is used to support different QoS markings?

A. IP precedence
B. DSCP
C. EXP
D. ToS
E. S
F. Label

Answer: C

Explanation:
MPLS EXP Marking
The three MPLS EXP (experimental) bits in the shim header of an input or output MPLS packet
header may be set or changed by a user configured value


QUESTION 4
On a Cisco IOS XR router, which mechanism protects the router resources by filtering and policing
the packets flows that are destined to the router that is based on defined flow-type rates?

A. LLQ
B. LPTS
C. Committed Access Rate
D. Control Plane Policing
E. Management Plane Protection
F. NetFlow
G. ACL

Answer: B

Explanation:
Local Packet Transport Services (LPTS) maintains tables describing all packet flows destined for
the secure domain router (SDR), making sure that packets are delivered to their intended
destinations.
The Low Latency Queueing feature brings strict priority queueing to Class-Based Weighted Fair
Queueing (CBWFQ).


QUESTION 5
When configuring LLQ (strict priority queue) on a traffic class using the Cisco IOS XR priority
command on a Cisco ASR9K router, which additional QoS command is required for this traffic class?

A. shape
B. police
C. random-detect
D. bandwidth

Answer: B

Explanation:
The Low Latency Queueing feature brings strict priority queueing to Class-Based Weighted Fair
Queueing (CBWFQ).

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