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642-812 Exam
Building Cisco Multilayer Switched Networks
科目编号：642-812
科目名称：Building Cisco Multilayer Switched Networks
考题数目：252 Q&As
更新日期：2009-11-27

642-812 考试是 Cisco 公司的 Building Cisco Multilayer Switched Networks 认证考试官方代号，Building Cisco Multilayer Switched Networks 认证作为全球IT领域专家 Cisco 热门认证之一，是许多大中IT企业选择人才标准的必备条件。 如果你正在准备 642-812 考试，为 Cisco Building Cisco Multilayer Switched Networks认证做最后冲刺，又苦于没有绝对权威的考试真题模拟， Pass4side 希望能助你成功。

1. Refer to the exhibit. What is the effect on the trust boundary of configuring the command mls qos trust cos on the switch port that is connected to the IP phone?
A. Effectively the trust boundary has been moved to the IP phone.
B. The host is now establishing the CoS value and has effectively become the trust boundary.
C. The switch is rewriting packets it receives from the IP phone and determining the CoS value.
D. The switch will no longer tag incoming voice packets and will trust the distribution layer switch to set the CoS.
E. RTP will be used to negotiate a CoS value based upon bandwidth utilization on the link.
Answer: A

2. Which statement about the Lightweight Access Point Protocol (LWAPP) is true?
A. LWAPP encrypts control traffic between the AP and the controller.
B. LWAPP encrypts user traffic with a x.509 certificate using AES-CCMP.
C. LWAPP encrypts both control traffic and user data.
D. When set to Layer 3, LWAPP uses a proprietary protocol to communicate with the Cisco Aironet APs.
Answer: A

3. Which statement is true about IP telephony calls?
A. A Voice over IP (VoIP) packet consists of the voice payload, IP header, TCP header, RTP header, and Layer 2 link header.
B. The voice carrier stream uses H.323 to set up, maintain, and tear down call endpoints.
C. Call control signaling uses Real-Time Transport Protocol (RTP) packets that contain actual voice samples.
D. The sum of bandwidth necessary for each major application, including voice, video, and data, should not exceed 75 percent of the total available bandwidth for each link.
Answer: D

4. Which statement is true about RSTP topology changes?
A. Any change in the state of the port generates a TC BPDU.
B. Only nonedge ports moving to the forwarding state generate a TC BPDU.
C. If either an edge port or a nonedge port moves to a block state, then a TC BPDU is generated.
D. Only nonedge ports moving to the blocking state generate a TC BPDU.
E. Any loss of connectivity generates a TC BPDU.
Answer: B