Cisco WS-X4604-GWY - VoIP Gateway Especificaciones descargar pdf (Pagina 57)

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Cisco IP Telephony Network Design Guide

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Chapter 2 Campus Infrastructure Considerations

IP Addressing and Management

Power Requirement Field

When the switch provides inline power to an IP phone, it has no way of knowing

how much power the phone needs (this varies by model). Initially, the switch

allocates 10W, then adjusts the delivered power according to the requirements

sent by the IP phone in the CDP message.

Auxiliary VLANs and Data VLANs

The new voice VLAN is called an auxiliary VLAN in the Catalyst software

command-line interface (CLI). In the traditional switched world, data devices

reside in a data VLAN. The new auxiliary VLAN is used to represent other types

of devices collectively. Today those devices are IP phones (hence the notion of a

voice VLAN), but, in the future, other types of non-data devices will also be part

of the auxiliary VLAN. Just as data devices come up and reside in the native

VLAN (default VLAN), IP phones come up and reside in the auxiliary VLAN, if

one has been configured on the switch.

When the IP phone powers up, it communicates with the switch using CDP. The

switch then provides the phone with its configured VLAN ID (voice subnet), also

known as the voice VLAN ID or VVID. Meanwhile, data devices continue to reside

in the native VLAN (or default VLAN) of the switch. A data device VLAN (data

subnet) is referred to as a port VLAN ID or PVID.

Figure 2-10 shows an IP phone and a PC in their respective VLANs.

Figure 2-10 Voice VLAN ID and Port VLAN ID

PC VLAN = 3

Phone VLAN = 200

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Cisco WS-X4604-GWY - VoIP Gateway Especificaciones Pagina 57