This value is the list of ports assigned to this secondary VLAN; if the VLAN type is isolated, these ports have complete Layer 2 separation from every other port in the private VLAN except promiscuous and trunk ports, while if the type is community, these ports can talk to each other and to promiscuous ports. Admins assign end-host ports to this list to enforce the appropriate isolation or community trust model for those devices. For example, assigning a set of guest-device ports to an isolated secondary VLAN would prevent those guests from communicating with each other directly.