Equipped with some of the router’s functions, the core switch layer 3 is a switch major in promote the data exchange in the large-scale local network. Assisted by its routing function, it achieves multiple transmission by one emission. Regular processes like data packets transmission are swiftly realized by its hardware, while route tasks such as the information update, the table maintenance, calculation and determination are operated by the software.
For the sake of a safe and convenient management, large-scale LAN shall be subdivided into small ones by its functions or regions, which aims at easing the broadcast storm. That makes the VLAN technology a widely used one in the network. Being a microphone for various VLANs, the router only, disadvantaged by the limited ports and a slow speed, can not achieve the inter network access under the booming mutual communication. The router-failed network improvement calls for the 3-layer switch designed for IP with simple interfaces and a powerful 2-layer packets processing ability. It is favorable for data routing and commuting in large-scale LAN. Not only can it work in the protocol third layer to replace a traditional router or to partially perform its duties, but also it possesses a competitive exchange speed of the second layer with a relatively low cost.