Cisco 300 Series Administration Manual page 240

VLAN Management
Voice VLAN
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)
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.
If the device is in Layer 2 system mode, it can synchronize with only
NOTE
VSDP capable switches in the same management VLAN. If the device is in
Layer 3 system mode, it can synchronize with VSDP capable switches that
are in the directly-connected IP subnets configured at the device.
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.
Voice VLAN QoS
Voice VLAN can propagate the CoS/802. 1 p and DSCP settings by using LLDP-
MED Network policies. The LLDP-MED is set by default to response with the Voice
QoS setting if an appliance sends LLDP-MED packets. MED-supported devices
must send their voice traffic with the same CoS/802. 1 p and DSCP values, as
received with the LLDP-MED response.
You can disable the automatic update between Voice VLAN and LLDP-MED and
use his own network policies.
Working with the OUI mode, the device can additionally configure the mapping
and remarking (CoS/802. 1 p) of the voice traffic based on the OUI.
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