VLAN Management
Voice VLAN
Cisco 500 Series Stackable Managed Switch Administration Guide Release 1.3 230
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• Auto Voice VLAN
In Auto Voice VLAN mode, the voice VLAN can be either the default voice
VLAN, manually configured, or learned from external devices such as
UC3xx/5xx and from switches that advertise voice VLAN in CDP or VSDP.
VSDP is a Cisco defined protocol for voice service discovery.
Unlike Telephony OUI mode that detects voice devices based on telephony
OUI, Auto Voice VLAN mode depends on Auto Smartport to dynamically
add the ports to the voice VLAN. Auto Smartport, if enabled, adds a port to
the voice VLAN if it detects an attaching device to the port that advertises
itself as a phone or media end points through CDP and/or LLDP-MED.
Voice End-Points
To have a voice VLAN work properly, the voice devices, such as Cisco phones and
VoIP endpoints, must be assigned to the voice VLAN where it sends and receives
its voice traffic. Some of the possible scenarios are as follows:
• A phone/endpoint may be statically configured with the voice VLAN.
• A phone/endpoint may obtain the voice VLAN in the boot file it downloads
from a TFTP server. A DHCP server may specify the boot file and the TFTP
server when it assigns an IP address to the phone.
• A phone/endpoint may obtain the voice VLAN information from CDP and
LLDP-MED advertisements it receives from their neighbor voice systems
and switches.
The device expects the attaching voice devices to send voice VLAN, tagged
packets. On ports where the voice VLAN is also the native VLAN, voice VLAN
untagged packets are possible.
Auto Voice VLAN, Auto Smartports, CDP, and LLDP
Defaults
By factory defaults, CDP, LLDP, and LLDP-MED on the device are enabled, auto
Smartport mode is enabled, Basic QoS with trusted DSCP is enabled, and all ports
are members of default VLAN 1, which is also the default Voice VLAN.
In addition, Dynamic Voice VLAN mode is the default to Auto Voice VLAN with
enabling based on trigger, and Auto Smartport is the default to be enabled
depending on Auto Voice VLAN.
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