VLAN Management
Voice VLAN
Cisco Sx350, SG350X, SG350XG, Sx550X & SG550XG Series Managed Switches, Firmware Release 2.2.5.x 226
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• 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, LLDP-MED, auto Smartport mode, and Basic QoS with
trusted DSCP is enabled. All ports are members of default VLAN 1, which is the default Voice
VLAN.
Voice VLAN Triggers
When the Dynamic Voice VLAN mode is Enable Auto Voice VLAN, Auto Voice VLAN
becomes operational only if one or more triggers occur. Possible triggers are static voice
VLAN configuration, voice VLAN information received in neighbor CDP advertisement, and
voice VLAN information received in the Voice VLAN Discovery Protocol (VSDP). If desired,
you can activate Auto Voice VLAN immediately without waiting for a trigger.
When Auto Smartport is enabled, depending on Auto Voice VLAN mode, Auto Smartport is
enabled when Auto Voice VLAN becomes operational. If desired, you can make Auto
Smartport independent of Auto Voice VLAN.
NOTE The default configuration list here applies to switches whose firmware version supports Auto
Voice VLAN out of the box. It also applies to unconfigured switches that have been upgraded
to the firmware version that supports Auto Voice VLAN.
NOTE The defaults and the voice VLAN triggers are designed to have no effect on installations
without a voice VLAN or on switches that have already been configured. You may manually
disable and enable Auto Voice VLAN and/or Auto Smartport to fit your deployment if needed.
Auto Voice VLAN
Auto Voice VLAN is responsible to maintain the voice VLAN, but depends on Auto Smartport
to maintain the voice VLAN port memberships. Auto Voice VLAN performs the following
functions when it is in operation:
• It discovers voice VLAN information in CDP advertisements from directly connected
neighbor devices.
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