单项选择题

WhichstatementistrueaboutIPtelephonycalls？（）……

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 H323 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.

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多项选择题WhichthreestatementsaretrueaboutthevoiceVLANfeatureonaCatalyst2950switch？（Choosethree.）（）

A. The CoS value is trusted for 802.1p or 802.1q tagged traffic.
B. The voice VLAN feature is disabled by default.
C. The IP phone accepts the priority of all tagged and untagged traffic and sets the CoS value to 4.
D. When the voice VLAN feature is enabled， all untagged traffic is sent according to the default CoS priority of the port.
E. PortFast is automatically disabled when a voice VLAN is configured.
F. The default CoS value for incoming traffic is set to 0.

多项选择题WhichthreeWLANstatementsaretrue？（Choosethree.）（）

A. A lightweight AP receives control and configuration from a WLAN controller to which it is associated.
B. A WLAN client that is operating in half-duplex mode will delay all clients in that WLAN
C. A dhoc mode allows mobile clients to connect directly without an intermediate AP
D. Another term for infrastructure mode is independent service set （IBSS）
E. The Aironet 1230 access point is an example of an access point that operates solely as a lightweight access point.
F. WLANs are designed to share the medium and can easily handle an increased demand of channel contention.

单项选择题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 theCoS
E. RTP will be used to negotiate a CoS value based upon bandwidth utilization on the link.

单项选择题Refer to the exhibit. Which statement is true about a voice VLAN？（）

A. Physically the voice network and the data network are separate.
B. The voice traffic will normally be on a different IP subnet than will the data traffic.
C. End user intervention is necessary to place the phone into the proper VLAN.
D. The same security policy should be implemented for both voice and data traffic.
E. The data VLAN must be configured as the native VLAN.

多项选择题Whichtwomulticastprotocolstatementsaretrue？（Choosetwo.）（）

A. Dense mode multicast requires explicit join messages from their members.
B. Dense mode multicast uses a push model to flood traffic throughout the network and then prunes the unwanted traffic.
C. Sparse mode multicast uses a pull model to send multicast traffic to where it is requested.
D. Sparse mode uses reverse path forwarding （RPF） to prune off redundant flows.
E. The primary use of sparse mode multicast is for test labs and router performance testing.