In the VLAN aggregation technology, multiple Sub-VLANs are used to isolate the wide recruitment area, and these Sub-VLANs are aggregated into a logical Super-VLAN. A company divides different departments into different Sub-VLANs because of the Sub-VLAN. VLAN not only includes physical connections, but also can establish a three-layer VLANIF interface, which can directly communicate with the external network on the three-layer.