642-845（Optimizing Converged Cisco Networks），屬於CCNP的一種考試，內容包括：描述基本的 VoIP 網絡的實施學習關於擁塞網絡的優化思想；學習實施集成的 QoS 服務特性；學習實施 QoS 的自動配置；學習優化 WLAN 的管理和安全。目前考取最新CCNP有兩種方案：方案1:640-901 + 642-812 + 642-825 + 642-845；方案2:642-892 + 642-825 + 642-845。CCNP 持有者有安裝和配置 100 到 500 個或者更多節點的網絡和排查故障的能力；能夠管理核心網絡的運作，以及綜合應用網絡邊緣的集成語音，無線以及安全方面的內容。

1. Which two QoS statements are true about the use of the SDM QoS wizard? (Choose two.)
A. Business-critical traffic includes VoIP and voice signaling packets.
B. SDM can be used to configure a basic QoS policy for incoming traffic on WAN interfaces and IPsec
tunnels.
C. SDM can provide QoS for real-time traffic and business-critical traffic.
D. SDM creates a custom-queuing (CQ) or a priority-queuing (PQ) policy.
E. SDM creates a low latency queuing (LLQ) service policy with its associated classes.
F. When allocating bandwidth, values can be entered in either bandwidth percentage or kilobytes per
second (kBps).
Answer: CE
2. Which two Cisco AutoQoS interface statements are true? (Choose two.)
A. AutoQoS is supported on Frame Relay multipoint subinterfaces.
B. AutoQoS is supported on low-speed ATM PVCs in point-to-point subinterfaces.
C. AutoQoS is supported on serial PPP and HDLC interfaces.
D. AutoQoS is supported only on Frame Relay main interfaces and not on any subinterface configuration.
Answer: BC
3. Which two wireless security statements are true? (Choose two.)
A. A TACACS+ server is required to implement 802.1x.
B. MIC protects against man-in-the-middle and replay attacks.
C. The 802.1x standard provides encryption services for wireless clients.
D. The AES (symmetric block cipher) is specified in the IEEE 802.11i specification.
E. The IEEE 802.11i specification uses RC4 as its encryption mechanism.
F. WPA requires TKIP and AES as encryption methods.
Answer: BD

642-845 考試是屬於CCNP的一種

11. What three statements are true about the various deployments of the 802.1x Extensible Authentication
Protocol (EAP)? (Choose three.)
Select 3 response(s).
A. EAP-FAST has the ability to tie login with non-Microsoft user databases.
B. EAP-TLS supports static passwords.
C. PEAP supports one-time passwords.
D. LEAP does not support multiple operating systems.
E. LEAP supports Layer 3 roaming.
F. PEAP does not work with WPA.
Answer: ACE
12. What are three security problems with Wi-Fi Protected Access (WPA)? (Choose three.)
Select 3 response(s).
A. WPA is based on the outdated IEEE 802.11i standard.
B. WPA uses RSN, which uses the same base encryption algorithm as RC4.
C. WPA requires a hardware upgrade that may not be supported by all vendors.
D. WPA uses TKIP, which uses the same base encryption algorithm as WEP.
E. WPA is susceptible to a DoS attack when it receives two packets in quick succession with bad MICs,
forcing the AP to shut down the entire Basic Service Set (BSS) for one minute.
F. WPA is susceptible to a security weakness when preshared keys are used.
Answer: DEF
13. Which three methods would help prevent critical network-traffic packet loss on high speed serial
interfaces? (Choose three.)
Select 3 response(s).
A. policy routing
B. increase link capacity
C. WRED
D. CBWFQ
E. LFI
F. WFQ
Answer: BCD
14. Interface congestion is causing drops in voice packets and TCP packets. The drops result in jerky
speech quality and slower FTP traffic flows. Which two technologies would proactively address the TCP
transfer rate and the voice problems? (Choose two.)
Select 2 response(s).
A. CBWFQ
B. LLQ
C. traffic shaping
D. WRED
Answer: BD
15. Which two statements about the DiffServ QoS model are true? (Choose two.)
Select 2 response(s).
A. DiffServ requires RSVP to set up a path through the network to accommodate the requested QoS.
B. Network traffic is identified by class, and the level of service is chosen for each class.
C. The DiffServ model relies on a fairly simple mechanism to provide QoS over a wide range of
equipment.
D. RSVP enables the DiffServ model to provide end-to-end QoS.
E. The DiffServ model is more scalable than the IntServ model.
F. The flow-based approach of the DiffServ model is ideal for large scalable implementations such as the
public Internet.
Answer: BE

ccnp 642-845

6. Voice activity detection (VAD) suppresses the transmission of silence patterns. On average, and
assuming that a link carries at least 24 calls, what percentage of total bandwidth could VAD save?
Select the best response.
A. 5
B. 15
C. 25
D. 35
E. 45
F. 55
Answer: D
7. Two sites are using a multisite centralized call processing model. The voice gateway on the remote
branch has lost IP connectivity to its Cisco CallManager server. Which feature enables the remote
gateway to take the role of the call agent during the WAN failure?
Select the best response.
A. automated alternate routing (AAR)
B. Cisco CallManager Attendant Console
C. real-time protocol (RTP)
D. Survivable Remote Site Telephony (SRST)
Answer: D
8. Refer to the exhibit. Both routers have been
9. To have the best possible voice quality and to utilize effectively the available bandwidth, which queuing
and compression mechanisms need to be used? (Choose two.)
Select 2 response(s).
A. class-based weighted fair queuing (CBWFQ)
B. low latency queuing (LLQ)
C. priority queuing (PQ) or custom queuing (CQ)
D. Real-Time Transport Protocol (RTP) header compression
E. TCP header compression
F. UDP header compression
Answer: BD
10. Which three statements about end-to-end delay are true? (Choose three.)
Select 3 response(s).
A. End-to-end delay is the sum of propagation delays, processing delays, serialization delays, and
queuing delays.
B. Coast-to-coast end-to-end delay over an optical link is about 20 ms.
C. Processing delay depends on various factors, which include CPU speed, CPU utilization, IP switching
mode, and router architecture.
D. Propagation and serialization delays are related to the media.
E. Propagation delay is the time it takes to transmit a packet and is measured in bits-per-second (bps).
F. Serialization delay is the time it takes for a router to take the packet from an input interface and put it
into the output queue of the output interface.
Answer: ACD

        CCNP  642-845  (Optimizing Converged Cisco Networks)考題由我們的專業團隊破解PROMETRIC或VUE考試系統數據包，經過資深IT認證講師和技術專家精心編輯整理。包括了當前最新的642-845考試問題，包括選擇題、多選擇題、實作（Lab）題.，全部附有正確答案。現在購買《642-845 考題》您將享受4倍（365天）免費升級服務時間，保證了您有充分時間完成考試.

1.What best describes an FXO interface?
A. analog trunks that provide the Survivable Remote Site Telephony (SRST) feature
B. analog trunks that provide VoIP gateway functionality
C. analog trunks that connect a gateway to plain old telephone service (POTS) device such as analog
phones, fax machines, and legacy voice-mail systems
D. analog trunks that connect a gateway to a central office (CO) or private branch exchange (PBX)
Answer. D
2 Which two steps are executed in the deployment of Cisco AutoQoS for Enterprise? (Choose two.)
A. The customer uses SNMP statistics to create the policy.
B. QoS policy templates are generated and installed on the interface.
C. RTP is used to generate the policy.
D. LLQ, cRTP, and LFI are used to automatically discover the policy.
E. The auto-generated policy is manually optimized before implementation.
F. Auto-discovery is used to determine what traffic is on the interface.
Answer. B F
4. Which two statements are true about the application of QoS in a converged network? (Choose two.)
A. End-to-end network delay times that exceed 50 ms for real-time traffic are considered unacceptable.
B. End-to-end network delay times that exceed 250 ms for real-time traffic are considered unacceptable.
C. End-to-end network delay is not a factor as long as the delay is consistent.
D. Some packet loss can be corrected by codec algorithms.
E. RSVP handles voice packet retransmission.
F. Fragmentation is a result of packet loss.
Answer. B D
5. What are two of the three predefined classes for the Cisco SDM wizard? (Choose two.)
A. business-critical
B. high priority
C. middle class
D. voice
E. best effort
F. scavenger
Answer. A E