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- CCNP Switching 642-813
51.
You have configured voice VLANs on Catalyst switch R1. Which two statements are true about the
operation of voice VLANs on this device? (Select two)
- 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.
- Answer & Explanation
- Report
Answer : [A, E]
Explanation :
Explanation :
52.
The Company network administrator has entered the "auto qos voip cisco-phone" command on
switch R1. What does this command do?
- A.It disables the trust boundary feature because the switch knows a Cisco IP phone is attached.
- B.The switch assigns a CoS value of 5 to incoming packets.
- C.If a Cisco IP phone is attached and removed, the switch continues to trust the CoS values as long as the switch is not rebooted.
- D.It turns on STP to see if a Cisco IP phone is attached.
- E.If a Cisco IP phone is attached, the switch trusts the CoS.
- F.None of the other alternatives apply.
- Answer & Explanation
- Report
Answer : [E]
Explanation :
Explanation :
| When the "auto qos voip cisco-phone" interface configuration command is entered, the trusted boundary feature is enabled. The trusted boundary feature uses CDP to detect the presence or absence of a Cisco IP Phone. When a Cisco IP Phone is detected, the ingress classification on the interface is set to trust the QoS label received in the packet. When a Cisco IP Phone is absent, the ingress classification is set to not trust the QoS label in the packet. The egress queues on the interface are also reconfigured. This command extends the trust boundary if an IP Phone is detected. |
53.
Which three statements are true about the voice VLAN configuration of the Catalyst switch?
(Choose three.)
interface Fastethernet0/1 switchport priority extend trust no ip address mls qos trust cos Actual Tests
- A.The packet priority received from a device that is connected to the phone will be unmodified.
- B.The packet priority received from a device that is connected to the phone will be overridden.
- C.Incoming CoS values in packets from the connected phone will be left unmodified.
- D.Packets without aCoS value that is set by the phone will be set to a value of 5.
- E.Incoming CoS values in packets from the connected phone will be reset to a value of 5.
- F.Packets without aCoS value that is set by the phone will be set to the default CoS value.
- Answer & Explanation
- Report
Answer : [A, C, F]
Explanation :
Explanation :
|
Traffic sent from the telephone to the switch is typically marked with a tag that uses the 802.1Q header. The header contains the VLAN information and the CoS 3-bit field, which determines the priority of the packet. For most Cisco IP Phone configurations, the traffic sent from the telephone to the switch is trusted to ensure that voice traffic is properly prioritized over other types of traffic in the network. By using the mls qos trust cos interface configuration command, you can configure the switch port to which the telephone is connected to trust the CoS labels of all traffic received on that port. You can connect a PC or other data device to a Cisco7960 IP Phone port. The PC can generate packets with an assigned CoS value. You can configure the switch to trust the priority of frames arriving on the IP phone port from connected devices. The "switchport priority extend trust" command is used to set the IP phone access port to trust the priority received from the PC or the attached device. |
54.
The Cisco AutoQoS feature is being used throughout the Company VOIP network. Which three
statements about this feature are true? (Select three)
- A.The "mls qos" global configuration command must be entered before configuring AutoQoS.
- B.CEF must be enabled.
- C.The "no auto qos voip" command is used to disable Cisco AutoQos and revoke all configurations generated by Cisco AutoQos.
- D.CDP must be enabled.
- E.SNMP must be enabled.
- Answer & Explanation
- Report
Answer : [B, C, D]
Explanation :
Explanation :
55.
VOIP is being implemented in the Company network and you need to assess the need for QoS.
Which of the following network problems would indicate a need to implement QoS features?
(Select three)
- A.Mis-routed packets
- B.Excess jitter
- C.Delay of critical traffic
- D.Packet loss due to congestion
- E.Data link layer broadcast storms
- F.FTP connections unsuccessful
- Answer & Explanation
- Report
Answer : [B, C, D]
Explanation :
Explanation :
| Loss, jitter, and delay are the three reasons for implementing QoS features on modern networks. Loss is when a packet disappears on a network. Jitter is a timing mismatch between two way traffic, and delay is when a packet takes too long to get somewhere. |
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