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The difference between layer 3 switch and Router

Although they all have routing functions.

However, the main function of the layer 3 switch is still data exchange, and its routing function is usually relatively simple, because it is mainly faced with a simple LAN connection, and the routing path is far less complex than the router. Its main use in LAN is to provide fast data exchange function, which meets the application characteristics of frequent data exchange in LAN.

The main function of the router is the routing function, and its routing function is more reflected in the interconnection between different types of networks, such as the connection between local area network and wide area network, the connection between networks with different protocols and so on. So routers are mainly used between different types of networks. Its main function is routing and forwarding, and its ultimate goal is to solve the connection of various complex routing path networks, so the routing function of routers is usually very powerful, not only between Lans of the same protocol, but also between Lans and WANs with different protocols. Its advantage lies in the functions of routers such as selecting the best route, load sharing, link backup and exchanging routing information with other networks. In order to connect with various types of networks, the interface types of routers are very rich, while layer 3 switches are generally only the same type of LAN interface, which is very simple.

Technically, there are obvious differences in packet switching operations between routers and layer 3 switches. Routers typically perform packet switching by a microprocessor-based software routing engine, while layer 3 switches perform packet switching through hardware. After routing the first data stream, the layer 3 switch will generate a mapping table of MAC address and IP address. When the same data flow passes again, it will directly pass through layer 2 instead of routing again according to this table, thus eliminating the network delay caused by routing by the router and improving the efficiency of packet forwarding. At the same time, the route lookup of layer 3 switch is aimed at data flow, it uses cache technology, it is easy to use ASIC technology to achieve, therefore, it can greatly save costs and achieve fast forwarding. On the other hand, the forwarding of the router adopts the longest matching method, and the implementation is complex, which is usually realized by software, and the forwarding efficiency is low.

Because of this, in terms of overall performance, the performance of layer 3 switch is much better than that of router, which is very suitable for LAN where data exchange is frequent. Although router has very powerful routing function, its packet forwarding efficiency is much lower than that of layer 3 switch, so it is more suitable for the interconnection of different types of networks where data exchange is not very frequent, such as the interconnection of LAN and Internet. If the router, especially the high-end router, is used in the local area network, it is to a considerable extent a waste (in terms of its powerful routing function), and it can not well meet the communication performance requirements of the local area network. affect the normal communication between subnets

To sum up, for multi-subnet connection in a local area network, it is best to choose a layer 3 switch, especially in an environment where data exchange between different subnets is frequent. On the one hand, it can ensure the communication performance requirements between subnets, on the other hand, it saves the investment of purchasing additional switches. Of course, if the communication between subnets is not very frequent, there is nothing wrong with using routers, and the purpose of securely isolating communication between subnets can be achieved. The details should be determined according to the actual needs.

The biggest difference between layer 3 switching and routing is that routing supports nat translation, while layer 3 does not. In the actual project, it is reflected in: the route directly connected to the optical fiber can be connected to the Internet, while the optical fiber connected to the layer 3 equipment is not able to access the Internet. Each port in the third layer has a dedicated mac address and a dedicated ASIC integrated circuit.

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