Basic concepts and comprehensive descriptions of layer-3 vswitches

Layer-3 switches are mainly used in simple LAN connections. Compared with routers, they are more convenient to use and quickly meet various networking requirements. In recent years, with the rapid development of Internet and information technology, people have increasingly felt that traditional routers have changed from the original traffic controllers to the current bottlenecks at intersections. Traditional routers work in isolated networks, isolated broadcasts, route forwarding, and firewalls. With the continuous development of the network, their workload is also growing rapidly.

Nowadays, VLAN (Virtual LAN) technology is widely used in networks for convenience of security and management. VLAN technology can logically isolate different network segments, ports, and even hosts. Communication between different VLANs must be forwarded through routers. Because of the large data traffic in the LAN, a large amount of information exchange between VLANs must be forwarded through routers. At this time, as the data traffic increases, routers become the bottleneck of the network.

To solve the bottleneck of the local area network, many enterprises use layer-3 switches to build local areas in their internal, school, and residential areas. Compared with the traditional concept, layer-3 switching is proposed. The traditional switching technology operates on the Layer 2-data link layer in the standard OSI network model, while the Layer 3 switching technology implements high-speed packet forwarding in the network model. To put it simply, layer-3 switching technology is layer-2 switching technology + layer-3 forwarding technology. A device with layer-3 switching is a layer-2 switch with layer-3 routing, but it is an organic combination of the two, it is not simply to overlay the hardware and software of a router device on a LAN switch.

Layer 3 vswitches and vrouters

The most fundamental difference between a layer-3 Switch and a router is that a layer-3 Switch also has a "routing" function, which is consistent with the routing function of a traditional router. However, layer-3 vswitches and vrouters are quite essentially different. A layer-3 switch is not equal to a vro and cannot replace a vro. Layer-3 switches are very suitable for LAN environments, while routers are very suitable for wide area networks. That is to say, layer-3 switches cannot adapt to wide-area network systems with different network topologies and different transmission protocols. Specifically, there are the following points:

1. The main functions of layer-3 switches and routers remain unchanged

Although both layer-3 vswitches and vrouters have routing functions, they cannot be equivalent. Currently, many broadband routers not only have routing functions, but also provide switch ports and hardware firewalls. However, they cannot be the same as switches or firewalls. Because the main functions of these routers are still routing functions, other functions are only their additional functions. The purpose is to make the devices more widely applied and more practical. The same is true for the layer-3 switch. It is still a switch product, but it has some basic routing functions. Its main function is data exchange. That is to say, it provides both data exchange and routing, but its main function is data exchange. The router only has the main function of routing forwarding.

2. layer-3 vswitches and vrouters use different places

Layer-3 switches are mainly used for simple LAN connections. Because of this, the routing function of the layer-3 switch is usually relatively simple, and the routing path is far less complex than that of the router. It is mainly used in LAN or provides fast data exchange function to meet the characteristics of frequent LAN data exchange applications.

Vrouters are different to meet different types of network connections. Although it is also suitable for LAN connections, its routing functions are more reflected in the interconnection between different types of networks, for example, the connection between the LAN and WAN and the connection between networks of different protocols. Therefore, routers are mainly used between different types of networks. Its main function is route forwarding. It is its ultimate goal to solve the connection of various complex routing paths. Therefore, the router's routing function is usually very powerful, not only applicable to LAN with the same protocol, it is more suitable for LAN and WAN networks with different protocols. Its advantage lies in the selection of the best routing, load balancing, link backup, and the exchange of routing information with other networks. In order to connect to various types of networks, vro interfaces are rich in types, while layer-3 vswitches are generally only LAN interfaces of the same type, which is very simple.

3. layer-3 vswitches and vrouters process data differently.

Technically speaking, there are significant differences between a router and a layer-3 Switch in Packet Exchange operations. Generally, a vro performs Packet Exchange by a microprocessor-based software routing engine, while a layer-3 vswitch performs Packet Exchange through hardware. After a layer-3 switch routes the first data stream, it will generate a ing table between the MAC address and IP address. When the same data flow passes again, the table is directly routed from the second layer instead of the second layer, which eliminates the network delay caused by router selection and improves the efficiency of packet forwarding. At the same time, the Routing Query of the layer-3 switch is for data streams. It uses the caching technology and ASIC Technology to easily implement it. Therefore, it can greatly save costs and achieve fast forwarding. Vro's forwarding adopts the longest matching method, which is complicated. It is usually implemented using software, and the forwarding efficiency is low.

Because of this, the performance of the layer-3 switch is far better than that of the router, which is very suitable for LAN with frequent data exchanges, however, its data packet forwarding efficiency is far lower than that of layer-3 switches. It is more suitable for the interconnection of different types of networks with less frequent data exchanges, such as the interconnection between LAN and the Internet. If a router, especially a high-end router, is used in a LAN, it is a waste of its powerful routing functions ), in addition, it cannot meet the requirements of LAN communication performance and affect the normal communication between subnets.

To sum up, there are major essential differences between layer-3 switches and routers. For multi-subnet connections in a LAN, it is best to select layer-3 switches, especially in environments with frequent data exchanges between different subnets. Although a router has powerful routing functions, its data packet forwarding efficiency is much lower than that of the layer-3 switch. It is more suitable for the interconnection of different types of networks with less frequent data exchanges, such as the interconnection between the LAN and the Internet.