Cisco Small Business 200 Series Administration Manual page 190

VLAN Management
Voice VLAN
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.
• If multiple neighbor switches and/or routers, such as Cisco Unified Communication (UC) devices, are
advertising their voice VLAN, the voice VLAN from the device with the lowest MAC address is used.
If connecting the device to a Cisco UC device, you may need to configure the port on the UC
NOTE
device using the switchport voice vlan command to ensure the UC device advertises its voice
VLAN in CDP at the port.
• It synchronizes the voice VLAN-related parameters with other Auto Voice VLAN-enabled switches,
using Voice Service Discovery Protocol (VSDP). The device always configures itself with the voice
VLAN from the highest priority source it is aware of. The priority is based on the source type and
MAC address of the source providing the voice VLAN information. Source type priority from high to
low are static VLAN configuration, CDP advertisement, and default configuration based on changed
default VLAN, and default voice VLAN. A numeric low MAC address is of higher priority than a
numeric high MAC address.
• It maintains the voice VLAN until a new voice VLAN from a higher priority source is discovered or until
the Auto Voice VLAN is restarted by the user. When restarted, the device resets the voice VLAN to
the default voice VLAN and restarts the Auto Voice VLAN discovery.
• When a new voice VLAN is configured/discovered, the device automatically creates it, and replaces
all the port memberships of the existing voice VLAN to the new voice VLAN. This may interrupt or
terminate existing voice sessions, which is expected when network topology is altered.
Auto Smartport works with CDP/LLDP to maintain the port memberships of the voice VLAN when voice
end-points are detected from the ports:
• When CDP and LLDP are enabled, the device sends out CDP and LLDP packets periodically to
advertise the voice VLAN to the voice endpoints to use.
• When a device attaching to a port advertises itself as a voice endpoint through CDP and/or LLDP, the
Auto Smartport automatically adds the port to the voice VLAN by applying the corresponding
Smartport macro to the port (if there is no other devices from the port advertising a conflicting or
superior capability). If a device advertises itself as a phone, the default Smartport macro is phone.
If a device advertises itself as a phone and host or phone and bridge, the default Smartport macro is
phone+desktop.
Cisco Small Business 200 Series Smart Switch Administration Guide
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