Each physical port has a parameter called PVID . Every 802.1Q port is assigned a PVID value that is of its native VLAN ID (default is VLAN 1). All untagged frames are assigned to the LAN specified in the PVID parameter. When a tagged frame is received by a port, the tag is respected. If the frame is untagged, the value contained in the PVID is considered as a tag. Because the frame is untagged and the PVID is tagged, this allows the coexistence, as shown in Figure 4, on the same pieces of cable of VLAN-aware bridge/stations and of VLAN-unaware bridges/stations. Consider, for example, the two stations connected to the central trunk link in the lower part of Figure 4. They are VLAN-unaware and they will be associated with VLAN C because the PVIDs of the VLAN-aware bridges are equal to VLAN C. Because the VLAN-unaware stations send only untagged frames, when the VLAN-aware bridge devices receive these untagged frames they assign them to VLAN C.