What Are the Differences Between Layer 3 Switches and Layer 2 Switches?

Layer 2 is a common switch.

Layer 3 with routing function.

In fact, there is no clear definition of whether the switch is Layer 2 or Layer 3, as long as the switch supports it, and you put it on the second layer on the network, then it is a Layer 2 switch, and if it is placed in the third layer, it is a Layer 3 switch. It is mainly determined by its location in the network.

1. The nature is different.

Layer 2 switches operate at Layer 2 (data link layer) in the OSI model, so they are called Layer 2 switches.

A Layer 3 switch is a switch with some router functions, which works at the third layer of the OSI network standard model: the network layer.

2. The purpose is different.

A Layer 2 switch is a data link layer device, which can identify the MAC address information in the data frame, perform ** based on the MAC address, and record these MAC addresses and corresponding ports in an internal address table.

The most important purpose of the Layer 3 switch is to speed up the data exchange within the large LAN, and the routing function is also for this purpose, which can be routed once and many times.

3. The principle is different.

How Layer 2 switches work.

If the Layer 2 switch has n ports, the bandwidth of each port is m, and the switch bus bandwidth exceeds n m, then the switch can achieve wire-speed switching.

Learn the MAC address of the machine to which the port is connected, write to the address table, and the size of the address table (generally expressed in two ways: one is buffer ram and the other is the numerical value of MAC table entries), and the size of the address table affects the access capacity of the switch.

Another is that Layer 2 switches generally contain ASIC (Application Specific Integrated Circuit) chips that are specifically designed to process data frames, so the speed can be very fast. Due to the different ASICs used by various manufacturers, the performance of products is directly affected.

The operation mechanism of the Layer 3 switch: The old instructions followed by the routing software have been changed, and the ASIC-specific embedded chip has been added to set the instructions. With the help of hardware, the existing routing table can be inspected, and it has the ability to refresh.

In the process of data transmission, the port chip accepts and identifies a certain information, and the layer 2 chip identifies the corresponding unique address. If a clear address is obtained, it will be given again; If it cannot be found, the information is deployed to the subsequent engine.

1. Layer 2 switching technology is relatively mature, and the layer 2 switch is a data link layer device, which can identify the MAC address information in the packet, carry out ** according to the MAC address, and record these MAC addresses and corresponding ports in an address table within itself.

2. The Layer 3 switch is a switch with some router functions, and the most important purpose of the Layer 3 switch is to speed up the data exchange within the large LAN, and the routing function is also for this purpose, which can be routed once and many times. For the regular process of packets, the hardware is implemented at high speed, and the functions such as routing information update, routing table maintenance, state split history routing calculation, route determination and other functions are implemented by software. Layer 3 switching technology is Layer 2 switching technology + Layer 3 ** technology.

First, the reference is different.

1. Layer 2 switch: It works in Layer 2 (data link layer) of the OSI model, so it is called a Layer 2 switch.

2. Layer 3 switches: switches with partial router functions, working at Layer 3 of the OSI network standard model.

Second, the functions are different.

1. Layer 2 switch: It is a data link layer device, which can identify the MAC address information in the packet, perform ** according to the MAC address, and record these MAC addresses and the corresponding ports in an internal address table.

2. Layer 3 switch: It is to speed up the data exchange within the large local area network, and the routing function is also for this purpose, which can be routed once and many times.

Third, the characteristics are different.

1. Layer 2 switch: The layer 2 switch has n ports, the bandwidth of each port is m, and the bus bandwidth of the switch exceeds n m, then the switch can achieve wire-speed switching.

2. Layer 3 switch: The regular process such as data packet ** is realized by the hardware at high speed, and the functions such as routing information update, routing table maintenance, routing calculation, and routing determination are implemented by software.