The maximum number of virtual local area networks (VLANs) is increased beyond the number provided solely with the VLAN ID, by a factor related to the number of wavelengths of a Wavelength Division Multiplexing (WDM) used by a network switching. An optical VLAN number (OVLAN ID) is a combination of the VLAN ID from the packet header and a path or wavelength ID (WL ID) that identifies a selected one of available wavelengths of a WDM transmission line. An Optical VLAN (OVLAN) conversion table stores data of the OVLAN ID, the VLAN ID and optical path ID, for an optical VLAN node.