A VLAN is a switched network that is logically segmented by functions, project teams, or applications, rather than on a physical or geographical basis. For example, all work stations and servers used by a particular workgroup team can be connected to the same VLAN, regardless of their physical connections to the network or the fact that they might be intermingled with other teams. You can use VLANs to reconfigure the network through software rather than physically unplugging and moving devices or wires.
When you use an IEEE 802.1Q trunk port, all frames are tagged except those on the VLAN configured as the native VLAN for the port. Frames on the native VLAN are always transmitted untagged and are normally received untagged. Therefore, when an Access Point (AP) is connected to the switchport, the native VLAN configured on the AP must match the native VLAN configured on the switchport.
Note: If there is a mismatch in the native VLANs, the frames are dropped.