多选题Which three statements are true about the voice VLAN feature on a Catalyst 2950 switch？ （Choose  three.）（）AThe CoS value is trusted for 802.1p or 802.1q tagged traffic.BThe voice VLAN feature is disabled by default.CThe IP phone accepts the priority of

第1题：

Which two statements are true about the protocols that are used for transmitting voice traffic？（）

• A、RTP multiplexing is used to keep multiple phone conversations separate
• B、RTP provides end-to-end delivery services for voice traffic
• C、UDP is used to ensure a reliable transmission from sender to receiver
• D、RTP is used to provide resource reservation for the voice stream
• E、UDP provides multiplexing

第2题：

Which two statements are true about voice VLANs？（）

• A、Voice VLANs are only used when connecting an IP phone and a host to distinct switch ports
• B、Access ports that are configured with voice VLANs will always trust the CoS that is received from IP phones
• C、Access ports that are configured with voice VLANs may or may not override the CoS value that is received from an IP phone
• D、Voice VLANs are configured using the switchport voice vlan vlan-ID interface configuration command
• E、Voice VLANs provide a trunking interface between an IP phone and an access port on a switch to allow traffic from multiple devices that are connected to the port
• F、Enabling Voice VLAN on a switch port will automatically configure the port to trust the incoming CoS markings

第3题：

Which three statements are true about the data traffic characteristics of voice traffic？ （）

• A、latency must be kept below 150 ms
• B、latency is not a concern as long as jitter is kept below 30 ms
• C、voice packets do not require a specific type of queuing
• D、voice packets are rather small
• E、voice packets require TCP for rapid retransmission of dropped packets
• F、voice packets require a fairly constant bandwidth reserved for voice control traffic as well as forthe voice payload

第4题：

Which three statements are true about the voice VLAN feature on a Catalyst 2950 switch？ （Choose  three.）（）  

• 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.

第5题：

Which three statements are true about terms in a policy?（）

• A、The order of the terms in a policy is irrelevant
• B、The action is specified in a then statement
• C、Ters are optional in a policy
• D、The match condition can be identified with a from statement
• E、Every policy must contain at least one term

第6题：

You have configured voice VLANs on Catalyst switch R1.  Which two statements are true about the  operation of voice VLANs on this device？ （）

• A、 When the voice VLAN feature is enabled， all untagged traffic is sent according to the default  CoS priority of the port.
• B、 Enabling voice VLANs enables the switch to create multiple queues for traffic that is entering a  port.
• C、 When voice VLANs are configured on a trunk link， UplinkFast must also be enabled.
• D、 Voice VLANs are configured to enable the switch to forward frames marked with the proper  CoS values over separate physical links.
• E、 Enabling voice VLANs enables the switch to forward frames with a specific 802.1P marking.

第7题：

The DAI feature has been implemented in the Company switched LAN.  Which three statements  are true about the dynamic ARP inspection （DAI） feature？ （）

• A、 DAI can be performed on ingress ports only.
• B、 DAI can be performed on both ingress and egress ports.
• C、 DAI is supported on access ports， trunk ports， EtherChannel ports， and private VLAN ports.  
• D、 DAI should be enabled on the root switch for particular VLANs only in order to secure the ARP  caches of hosts in the domain.
• E、 DAI should be configured on all access switch ports as untrusted and on all switch ports connected to other switches as trusted.
• F、 DAI is supported on access and trunk ports only.

第8题：

Which two statements are true about analog to digital conversion of voice signals for use in digital telephony networks？（）

• A、The three required steps in the analog to digital conversion are sampling，encoding，and compression.
• B、The three required steps in the analog to digital conversion are sampling，quantization，and compression.
• C、The three required steps in the analog to digital conversion are sampling，quantization，and encoding.
• D、The output of the sampling process is a pulse code modulation （PCM） signal.
• E、The output of the sampling process is a pulse amplitude modulation （PAM） signal.

第9题：

Which two statements are true about the configuration of voice VLANs？（）

• A、Static secure MAC addresses can be configured in conjunction with voice VLANs.
• B、PortFast is automatically enabled when voice VLANs are configured.
• C、PortFast must be manually configured when voice VLANs are configured.
• D、Voice VLANs are typically configured on uplink ports.
• E、Voice VLANs are typically configured on access ports.

第10题：

Which statement is true about voice VLANs？ （）

• A、When the voice VLAN feature is enabled， all untagged voice and data traffic is sent through the voice VLAN.
• B、The voice VLAN feature is enabled by default.
• C、The IP phone overrides the priority of all incoming data traffic （tagged and untagged） and sets the CoS value to 0.
• D、The default CoS value is 1 for incoming voice and data traffic.