(With the rapid development of network technology, L3, L4 switching has been very mature. The switching technology is also used more and more widely in the Internet, and the full switching network has become very common. In these networks, the use of VLANs is essential. 1. Description of VLAN (VirtualLANs) ………… 2. VTP (VLANTrunkingProtocol)………………3. Spanning-TreeProtocol………………)