642-887は中級者向け試験です。
642-887試験はMPLS テクノロジーおよび MPLS-TE サービスの概念と実装に関する知識を確認します。
642-887試験について最新の情報を伝えられたいですか？
勉強形態は独学の初心者として、Passexamの642-887問題集を使用しなければなりません。
弊社の
642-887勉強資料の合格率は100パーセントに達したので、絶対あなたが試験を受かることに重要な助けになれます。
642-887認定試験情報：
試験番号：642-887
試験名称：Implementing Cisco Service Provider Next-Generation Core Network Services
関連資格：CCNP Service Provider
試験時間：90 分
出題形式 ： 単一選択,複数選択,リスト選択(単一),リスト選択(複数),ドラッグ＆ドロップ
問題数：75 問
試験言語：英語
試験登録：Pearson VUE
合格点 ：700点
642-887出題内容：
1.0 サービス プロバイダー IP NGN 環境における QoS 38%
2.0 サービス プロバイダー IP NGN 環境における MPLS/LDP 32%
3.0 サービス プロバイダー IP NGN 環境における MPLS トラフィック エンジニアリング 22%
4.0 転送テクノロジー 8%
英語は、CCNP Service Provider取るときの参考書を読んで慣れてたのでそれが642-887（Implementing Cisco Service Provider Next-Generation Core Network Services）試験でも生きました。
とはいっても、Passexamで予習していれば余裕だと思います。
642-887認定試験と同様に、単一選択、複数選択、リスト選択(単一)、リスト選択(複数)、ドラッグ＆ドロップの質問は、あなたが試験に合格するのに役立ちます。
1.Which three conditions can occur when metering traffic using a dual token bucket traffic policing QoS
mechanism on Cisco routers? (Choose three.)
A. conform
B. pass
C. violate
D. exceed
E. burst
F. matched
Answer: A,C,D
2.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) ? 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.
3.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.
4.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
5.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).
