TP-Link T3700G-28TQ T3700G-28TQ V1 UG - Page 101
The Elements of a Private VLAN, Promiscuous port, Host port, Primary VLAN, Secondary VLAN
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Private VLAN adopts Layer 2 VLAN structure. A Private VLAN consists of a Primary VLAN and a Secondary VLAN, providing a mechanism for achieving layer-2-separation between ports. For uplink devices, all the packets received from the downstream are without VLAN tags. Uplink devices need to identify Primary VLANs but not Secondary VLANs. Therefore, they can save VLAN resources without considering the VLAN configuration in the lower layer. Meanwhile, the service provider can assign each user an individual Secondary VLAN, so that users are separated at the Layer 2 level. Private VLAN technology is mainly used in campus or enterprise networks to achieve user Layer-2-separation and to save VLAN resources of uplink devices. The Elements of a Private VLAN Promiscuous port: A promiscuous port connects to and communicates with the uplink device. The PVID of the promiscuous port is the same with the Primary VLAN ID. One promiscuous port can only join to one Primary VLAN. Host port: A host port connects to and communicates with terminal device. The PVID of the host port is the same as the Secondary VLAN ID. One host port can only belong to one Private VLAN. There are two types of host ports: Isolated port-An isolated port has complete Layer 2 separation from all other ports within the same private VLAN except for the promiscuous ports. Private VLANS block all traffic to isolated ports except traffic from promiscuous ports. Traffic received from an isolated port is forwarded only to promiscuous ports. Community port - Community ports communicate among themselves and with the promiscuous ports. These interfaces are isolated at Layer 2 from all other interfaces in other communities or isolated ports within their private VLAN. Primary VLAN: A Private VLAN has one Primary VLAN and one Secondary VLAN. Primary VLAN is the user VLAN uplink device can identify but it is not the actual VLAN the end user is in. Every port in a private VLAN is a member of the primary VLAN. The primary VLAN carries unidirectional traffic downstream from the promiscuous ports to the host ports and to other promiscuous ports. Secondary VLAN: .Secondary VLAN is the actual VLAN the end user is in. Secondary VLANs are associated with a primary VLAN, and are used to carry traffic from hosts to uplink devices. There are two types of secondary VLANS: Isolated VLAN-The VLAN that an isolated port is associated with is called isolated VLAN. Each isolated VLAN must bind to a primary VLAN. Community VLAN-The VLAN that a community port is associated with is called community VLAN. Each community VLAN must bind to a primary VLAN. Features of Private VLAN 1. A Private VLAN contains one Primary VLAN and one Secondary VLAN. 2. A VLAN can not be set as the Primary VLAN and Secondary VLAN simultaneously. 3. A Secondary VLAN can only join one private VLAN. 90