Detailed explanation: What is a network switch?

A network switch is a device that extends a network and provides more connection ports in a subnet. It can connect devices within the network and forward data packets to or from these devices.

Network switch type

In a broad sense, network switches are divided into WAN switches and LAN switches. WAN switches are mainly used in the telecommunications field to provide a basic communication platform. LAN network switches are used in local area networks to connect terminal devices such as PCs and network printers.

According to the network structure, network switches are divided into three types: access switches, aggregation switches and core switches. Among them, core layer switches all adopt chassis-type modular design, and basically all of them have been designed with 1000Base-T modules to match them. The Ethernet switches that support 1000Base-T at the access layer are basically fixed-port switches, mainly with 10/100M ports, and provide 1000Base-T uplink ports in the form of fixed ports or expansion slots. The aggregation layer 1000Base-T switches have both chassis-type and fixed-port designs, which can provide multiple 1000Base-T ports, and generally can also provide other forms of ports such as 1000Base-X. Access layer switches and aggregation layer switches can provide complete LAN solutions for small and medium-sized enterprises.

According to the transmission speed, it can be divided into Fast Ethernet switch, Gigabit Ethernet switch, 10Gb Ethernet switch, 25Gb Ethernet switch, 40Gb Ethernet switch and 100Gb Ethernet switch.

According to the OSI model, network switches are divided into six types: Layer 2 switches, Layer 3 switches, Layer 4 switches, Layer 5 switches, Layer 6 switches, and Layer 7 switches. Layer 2 switches based on MAC addresses are widely used and are used in the access layer and aggregation layer. Layer 3 switches work based on IP addresses and protocols and are commonly used in the core layer and a small amount in the aggregation layer. Layer 4 and above switches are more commonly used in Internet data centers.

According to the switch management characteristics, it can be divided into managed switches and unmanaged switches. The difference between managed switches and unmanaged switches is whether they support SNMP (Simple Network Management Protocol), RMON (Remote Network Monitoring) and other protocols. Managed switches support network monitoring and traffic analysis, but the price is very high. For medium and large networks, managed switches should be selected at the aggregation layer, and at the access layer, it depends on the application requirements. All core layer switches are managed switches.

Managed switches usually have a remotely accessible console (command line or web interface) so administrators can make changes or adjustments from different physical locations. In contrast, unmanaged switches are "plug and play." They allow Ethernet devices to automatically communicate with each other using auto-negotiation to determine parameters such as data transmission speed and whether to use half-duplex or full-duplex mode. In short, managed switches can adjust the switch configuration based on system requirements and monitor the status of the switch, while unmanaged switches come with a fixed configuration that does not allow any changes to this configuration.

Depending on whether the switch supports stacking, it is divided into stackable switches and non-stackable switches. The purpose of stacking design is to increase port density. When using standalone switches, each switch is managed, troubleshooted, and configured as a separate entity. In contrast, stackable switches provide a way to simplify and improve network availability. A stackable switch is a full-featured network switch that can work independently but can also be configured to work with one or more other network switches.

Features of switches

The main functions of a switch include physical addressing, network topology, error checking, frame sequence, and flow control. Currently, switches also have some new features, such as support for VLAN (virtual local area network), support for link aggregation, and some even have firewall functions.

Learning function

The Ethernet switch learns the MAC address of the device connected to each port, assigns the address to the corresponding port, and stores it in the MAC address table cached in the switch.

Loop Elimination

When switches contain redundant loops, Ethernet switches use the Spanning Tree Protocol to prevent loops while allowing alternate paths to exist.

Forwarding/Filtering

When the destination address of a data frame is mapped in the MAC address table, it is forwarded to the port adjacent to the destination node instead of all ports (if the data frame is a broadcast frame/multicast frame, it is forwarded to all ports).

In addition to connecting networks of the same type, switches can also interconnect networks of different types (such as Ethernet and Fast Ethernet). Many switches now provide high-speed connection ports that support Fast Ethernet or FDDI, which are used to connect other switches in the network or provide additional bandwidth for key servers that occupy a large amount of bandwidth.

Generally speaking, each switch port is used to connect to a separate network segment, but sometimes in order to provide faster access speed, some important network computers may be directly connected to the switch port. In this way, the key servers and main users of the network can get faster access speed and support larger information flow.