Refer to the exhibit.
Which three statements are true about the voice VLAN configuration of the Catalyst switch?
(Choose three.)
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 a CoS 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 a CoS value that is set by the phone will be set to the default CoS value.
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 Cisco 7960 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.
Reference:
http://www.cisco.com/en/US/docs/switches/lan/catalyst2940/software/release/12.1_19_ea1/c
onfiguration/guide/swvoip.html