Chapter 14
Voice
See the following sections to configure and use these features:
■ 14-1: Voice Ports: Covers the commands necessary to configure switched Ethernet
ports for IP telephony
■ 14-2: Voice QoS: Presents guidelines and configuration suggestions that provide end-
to-end quality of service (QoS) in a campus network
14-1: Voice Ports
■ Inline power is provided to a powered device as follows:
■ A phantom-powered device can be detected as a switch port becomes active.
■ A powered device loops the transmit and receives pairs back so that the switch
detects its own 340 kHz test tone.
■ Power is applied to the port if the device is present; no power is applied if a nor-
mal Ethernet device is connected.
■ Inline power is provided over pairs 2 and 3 (RJ-45 pins 1,2 and 3,6) at 48V DC.
■ Inline power is available on a variety of Catalyst switch products.
■ Powered devices can connect to a wall power adapter and the power patch panel.
The devices use the patch panel as a backup power source.
■ Power is provided over pairs 1 and 4 (RJ-45 pins 4,5 and 7,8) at 48V DC.
■ A Catalyst switch can send instructions to a Cisco IP Phone on how to present
frames from its voice and data ports. This is done through Cisco Discovery Protocol
(CDP) messages.
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