Private Vlans - Dell Networking N4000 Series Configuration Manual

default PVID of the port, and the voice traffic is received tagged with the
predefined 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 or CDP 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 higher priority.
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.

Private VLANs

Private VLANs partition a standard VLAN domain into two or more
subdomains. Each subdomain is defined by a primary VLAN and a secondary
VLAN. The primary VLAN ID is the same for all subdomains that belong to a
particular private VLAN instance. The secondary VLAN ID differentiates the
subdomains from each other and provides layer 2 isolation between ports on
the same private VLAN.
The following types of VLANs can be configured in a private VLAN:
• Primary VLAN—Forwards the traffic from the promiscuous ports to
isolated ports, community ports and other promiscuous ports in the same
private VLAN. Only one primary VLAN can be configured per private
VLAN. All ports within a private VLAN share the same primary VLAN.
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Configuring VLANs