Ports on a secondary Private VLAN that communicate only with Promiscuous ports are

p.29 of vsphere-esxi-vcenter-server-50-networking-guide.pdf:

A private VLAN is identified by its primary VLAN ID. A primary VLAN ID can have multiple secondary
VLAN IDs associated with it. Primary VLANs are Promiscuous, so that ports on a private VLAN can
communicate with ports configured as the primary VLAN. Ports on a secondary VLAN can be either
Isolated, communicating only with promiscuous ports, or Community, communicating with both
promiscuous ports and other ports on the same secondary VLAN.