Cisco Small Business 200 Series Administration Manual page 191

VLAN Management
Voice VLAN
Voice VLAN QoS
Voice VLAN can propagate the CoS/802.1p 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/802.1p 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/802.1p)
of the voice traffic based on the OUI.
By default, all interfaces are CoS/802.1p trusted. The device applies the quality of service based on the
CoS/802.1p value found in the voice stream. For Telephony OUI voice streams, you can override the
quality of service and optionally remark the 802.1p of the voice streams by specifying the desired CoS/
802.1p values and using the remarking option under Telephony OUI.
Voice VLAN Constraints
The following constraints exist:
• Only one Voice VLAN is supported.
• A VLAN that is defined as a Voice VLAN cannot be removed
In addition the following constraints are applicable for Telephony OUI:
• The Voice VLAN cannot be VLAN1 (the default VLAN).
• The Voice VLAN cannot be Smartport enabled.
• The Voice VLAN QoS decision has priority over any other QoS decision, except for the Policy
decision.
• A new VLAN ID can be configured for the Voice VLAN only if the current Voice VLAN does not have
candidate ports.
• The interface VLAN of a candidate port must be in General or Trunk mode.
• The Voice VLAN QoS is applied to candidate ports that have joined the Voice VLAN, and to static
ports.
• The voice flow is accepted if the MAC address can be learned by the Forwarding Database (FDB). (If
there is no free space in FDB, no action occurs).
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