Build a large-scale bureau network: layer-3 switch technology and products (1)

With the rapid development of the Interconnection Network and the advancement of social information, the network is rapidly developing in terms of scale and speed. The speed of the local area network has grown from 10 mbit to 100 mbit, now, Gigabit Ethernet is widely used. In the past, we used shared LAN to share the same network transmission medium. CSMA/CD, token ring, and token bus were typical access control methods. Exchange LAN refers to the data link layer as the switching unit, which fundamentally solves the speed problem of shared Ethernet. It allows multiple nodes to communicate at the same time, and each node can monopolize the transmission channel and bandwidth. The speed problem between the ground layer and the second layer has been solved. However, the traditional router technology has not made great progress, and it is difficult to meet people's needs for high speed. Therefore, the concept of layer-3 switching technology is put forward. It is a router because it can operate on the third layer of the network protocol. It is a router that understands the device and can act as a route. It is a switch because it is extremely fast, almost reached the second-level switching speed. This is also the topic of this Article. What is layer-3 switching technology. Let's first introduce the OSI model, which is widely recognized as the Open System Interconnection Model OSI of the International Organization for Standardization (ISO). It is a hierarchical network architecture, divide a network system into layer-7 definitions. We will only introduce the lower three layers. The above four layers all involve specific applications.
First Layer Physical Layer:
The physical layer is the basis for data transmission. It consists of enough hardware to form a communication channel for data transmission. The physical layer only transmits bit streams, specifying the mechanical and electrical characteristics of the channel and the interface between the last layer. The modem MODENM and HUB that are frequently used in our door are both physical layer network devices.
Layer 2 data link layer:
The data link layer provides Data Link Control and error verification functions, turning unreliable physical links into reliable data links. The communication at the data link layer is based on the premise that we are familiar with the exchange technology, that is, the pure exchange technology implemented by the switch. The traditional switch L2 Switch is a typical network device at the data link layer, its predecessor is the bridge, which works on the second layer of the network. One of its functions is to isolate the network broadcast storm. A vswitch can only connect to a computer in the same subnet. If the IP address of a computer is not in the same subnet, only the vswitch can not implement communication, but also the vro on the third layer.
Layer 3 network layer:
The network layer can be said to be a crucial layer in the OSI model. It plays an important role in connecting up and down. As mentioned above, it is responsible for communication between subnets, the famous TCP/IP protocol is the protocol at the network layer. The router with the routing function is required for communication between two subnets. If a data packet is sent from a subnet to a computer node in another subnet, the transmission path is calculated through the router.
We have already introduced the bottom three layers of OSI. In fact, the 'l3 'in layer-3 switching technology refers to the layer-3 network layer of OSI. It is relative to the traditional layer-2 exchange technology. Since a layer-3 switch is in the same layer, it must be used for connection and communication between subnets, that is, it has the routing function. It implements data packet notification forwarding on the third layer. In simple terms, layer-3 switching technology = Layer-2 switching technology + layer-3 routing function, we can also understand it as three-tier switch = two-tier switch + traditional router. A layer-3 Switch has the performance and functions of a vswitch.
Applicable status of L3 switches:
L2 switches are mainly used in small local area networks with around 20 machines. In this environment, the speed of the network broadcast package is not very significant. The Quick Switch Feature of L2 switches, multiple access ports, and low prices provide a perfect solution for small network users. In such a small network, there is no need to introduce the routing function to increase the management difficulty and cost, so there is no need to use a router, of course, there is no need to use a layer-3 switch.
In a large LAN, campus network, and core backbone network, layer-3 switches must be used. If no layer-3 switch is used, all computers are in the same subnet. A broadcast storm can paralyze the entire network. And the security is poor. Maybe you can use a traditional router. Although vrouters can isolate broadcast performance. A layer-3 Switch uses a hardware exchange mechanism to implement the IP routing function. Its Optimized Routing software improves the routing efficiency and solves the routing speed problem of the traditional router software. As mentioned above, layer-3 switches also play an important role in connecting to subnets while ensuring speed. In order to reduce the number of computers in the same network, it cannot be too large. Therefore, we need to add multiple IP subnets to prevent broadcast storms. The tasks between subnets will also depend on the layer-3 switch. It is also because traditional routers are too weak in capabilities. The price of a gigabit router is unacceptable. Generally, the price of a third-level switch is around 10000 yuan, while that of a gigabit-level router is within the "" range.
In addition to cost-effective, layer-3 vswitches have scalable lines. A layer-3 vswitch is connected to multiple subnets. A subnet only establishes a logical connection with the layer-3 Switching Module and does not require a port to be added to a traditional router. If you need to add network devices, you can directly expand the devices without modifying the original network layout and the original devices because you have reserved various extension module interfaces to protect your original investment. High Security is also an important attraction for layer-3 switches. A layer-3 switch must be at the core network layer, which is the target of cyberattacks. In terms of software, a high-reliability firewall can be configured to block unidentified data packets. In addition, the access list can be set to restrict internal users to access some special IP addresses. In addition, it can prevent illegal external visitors from accessing the internal network.