According to theFortiSwitchOS 7.6 Administration Guideand theFortiSwitch 7.6 Study Guide, Private VLANs (PVLANs) provide a mechanism to partition a regular VLAN (the Primary VLAN) into sub-VLANs to control Layer 2 traffic flow within the same broadcast domain.
In a multi-tenant environment requiring strict security, anIsolated VLAN (Option C)is the correct choice to prevent lateral communication between servers. The documentation specifies that ports within an Isolated VLAN are completely blocked from communicating with any other ports in the same Isolated VLAN or any Community VLANs. This effectively eliminates the risk of "east-west" traffic or lateral movement between tenant servers, even if they reside in the same physical switch and logical subnet.
However, the architecture of PVLANs ensures that these isolated ports can still communicate with Promiscuous ports. In this scenario, the shared FortiGate firewall would be connected to a Promiscuous port within thePrimary VLAN (Option D). This allows all tenant servers in the Isolated VLAN to send and receive traffic to the FortiGate for internet access and centralized security filtering, while remaining invisible to one another at the hardware layer.
Community VLANs (Option B)would be inappropriate for this specific requirement because ports within a Community VLANcancommunicate with each other, which violates the requirement for complete isolation between all servers. Therefore, the combination of an Isolated VLAN for the servers and a Promiscuous port for the firewall is the standard design for multi-tenant isolation in FortiSwitchOS 7.6.