When a VLAN is associated with the Voice VLAN port, then the VLAN ID
information is passed onto the VoIP phone using the LLDP-MED
mechanism. By this method, the voice data coming from the VoIP phone
is tagged with the exchanged VLAN ID. Untagged data arriving on the
switch is given the default PVID of the port, and the voice traffic is
received tagged with the pre-defined VLAN. As a result, both kinds of
traffic are segregated in order to provide better service to the voice traffic.
When a dot1p priority is associated with the Voice VLAN port instead of a
VLAN ID, then the priority information is passed onto the VoIP phone
using the LLDP-MED mechanism. By this method, the voice data coming
from the VoIP phone is tagged with VLAN 0 and with the exchanged
priority; thus regular data arriving on the switch is given the default
priority of the port (default 0), and the voice traffic is received with a
You can configure the switch to override the data traffic CoS. This feature
can override the 802.1 priority of the data traffic packets arriving at the port
enabled for Voice VLAN. Therefore, any rogue client that is also connected to
the Voice VLAN port does not deteriorate the voice traffic.
Voice VLAN and LLDP-MED
The interactions with LLDP-MED are important for Voice VLAN:
LLDP-MED notifies the Voice VLAN component of the presence and
absence of a VoIP phone on the network.
The Voice VLAN component interacts with LLDP-MED for applying
VLAN ID, priority, and tag information to the VoIP phone traffic.
Additional VLAN Features
The PowerConnect M6220, M6348, M8024, and M8024-k switches also
support the following VLANs and VLAN-related features:
VLAN routing interfaces — See "Configuring Routing Interfaces" on
Guest VLAN — See "Configuring 802.1X and Port-Based Security" on