How to Implement LAN switch control

All sites in a LAN are connected to a hub or LAN switch, and the frame is forwarded to all ports or an upstream port belonging to the same VLAN except the source port.

With the improvement of computer performance and the increasing traffic, traditional local area networks are getting more and more out of their load. The exchange Ethernet technology has emerged, greatly improving the performance of local area networks. A network switch can significantly increase the bandwidth and establish a geographically dispersed network.

Each port of a LAN switch can transmit information in parallel, securely, and in real time. It features stable performance, flexible structure, easy installation, and easy management. It can meet the needs of CEN and telecom operators for broadband access, the management unit allows you to assign switches to various working modes.

With the demand for security and high bandwidth in network applications. Vswitches are widely used. The vswitch uses the ROX bus of the AL101 chip to connect three eight-port switching chips to form a 24-port switch, meeting users' requirements for multiple switching ports.

1.1 circuit performance requirements

High-Speed PCB boards of switches have high requirements on EMC and ESD. It uses a high-speed clock of 75 MHz and 50 MHz. The accuracy of the crystal oscillator must be smaller than 50 ppm, and the clock must be sent to different chips through the clock distribution circuit, the phase difference between the clock to be allocated is less than 2ns.

A lan switch has 24 10/100 M Adaptive ports, and each port can achieve line rate switching. You can set the port at a rate of 10/100 M, full/half duplex, traffic control, static MAC address, image, and VLAN as needed.

1.2 principle diagram of vswitch

The switch technology of the local area network adopts the storage-forwarding mode, which consists of the Interface Unit, switching unit, management unit, lamp display unit and Power Interface Unit. The Block Diagram 1 is shown in.

After receiving an Ethernet frame data packet, the RJ45 interface is sent to the PHY (physical interface chip) after the transformer isolation and impedance matching. In this chip, the analog signal is converted to the digital signal of the RMII interface, obtain information such as the link status, conflict, whether the information is too long, and the speed.

Data enters the switching chip (consisting of three chips, forming a loop through the ROX bus to exchange data between the three chips ), the switching chip obtains the destination address and Source Address of the data and performs error verification on the Ethernet frame.

The switch chip saves the source address in its MAC address table, and then matches the destination address with the address in the MAC address table to obtain the corresponding port for data forwarding. If the destination port is in the same swap chip, data is retrieved from SGRAM and forwarded to the corresponding port;

If the destination port is not in the same switch chip, data is transmitted to the corresponding switch chip through the ROX bus and then forwarded out. If the target address is not found in the MAC address table, the frame is forwarded to all ports belonging to the same VLAN except the source port or an uplink port (related to the settings of the SWAp chip register ).

The lamp display is provided by PHY. The lamp display allows you to observe the working rate, connection, and data sending and receiving of each port. During each boot or reset, the swap chip first reads the content of the external EEPROM to initialize the swap chip register. The content of the switch chip register can be read and written through the Management Program of the PC or the super terminal of the PC to control or read the working configuration of the LAN switch.

1. Correct Interpretation and test of vswitch Port
2. Summarize the market status of high-end Switches
3. Focuses on core layer switch faults
4. PythonAndroid
5. Let's talk about the stacking of Ethernet switches.