VLANs used to divide the Broadcast Domains. With this division, different departments, networks are isolated each other and become another Broadcast Domain. Sometimes, this separation is not enough and additional separation is needed. Private VLANs (pVLANs) are used at these times. Here, we will focus on the basics of Private VLANs. In another lesson, we will also learn How to Configure Private VLANs on Cisco switches.
Basically we can say that Private VLANs are sub-VLANs or VLAN of VLANs. With Private VLANs, in the same Broadcast Domain, network can be divided again. This time, the network is still one Broadcast Domain but as divided.
In Private VLANs (pVLANs), there are two different sub VLAN types. These are, Primary VLAN and Secondary VLANs. Primary VLAN use a VLAN ID that is same for all the other sub VLANs. Secondary VLANs are also use VLAN ID. But Secondary VLANs’ VLAN ID provides the separation of different sub VLANs.
Secondary VLANs has also two sub type VLANs. These are Community VLANs and Isolated VLANs.
Let’s pick up all VLAN types of a Private VLANs :
Primary VLAN is a normal VLAN as we discussed before. It is the upper VLAN now. You can use one Primary VLAN per Private VLAN and all the other port types are member of this Primary VLAN.