There are three operations in the working principle of the switch: 1. Drop, that is, discard when the host under this port accesses the host under this port; 2. Forward, that is, when the host under a certain port accesses Forwarding when a host under a certain port is known; 3. Diffusion, that is, when a host under a certain port accesses a host under an unknown port, it needs to be flooded.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
A switch is a network device used for forwarding electrical (optical) signals. It can provide an exclusive electrical signal path for any two network nodes connected to the switch. The most common switch is an Ethernet switch. The switch works on the second layer of the OSI reference model, the data link layer. The switch has a high-bandwidth back bus and internal switching matrix that can transmit data between multiple port pairs at the same time. The transmission modes of the switch include full-duplex, half-duplex, and full-duplex/half-duplex adaptive.
Working principle
Address table
The port address table records the host address under the port. MAC address. The port address table is automatically established after the switch is powered on,
is saved in RAM, and is automatically maintained.
The principle of a switch to isolate conflict domains is based on its port address table and forwarding decisions.
Forwarding decision
The forwarding decision of the switch has three operations: discarding, forwarding and flooding.
Discard: Discard when the host under this port accesses the host under this port.
Forwarding: forward when a host under a certain port accesses a known host under a certain port.
Diffusion: When a host under a certain port accesses a host under an unknown port, it needs to be flooded.
Every operation must record the MAC address of the sending end to prepare for access by other hosts.
Lifetime
Lifetime is the lifespan of an entry in the port address list. Each entry starts counting down after it is created, and the timer must be refreshed every time
data is sent. For hosts that do not send data for a long time, their MAC address entries will be deleted at the end of the lifetime.
So the port address table always records the MAC address of the most active host.
(4) It should be said that there is a lot worth learning about switches. Here we mainly introduce the switch structure and networking methods. Since the 1910s, network applications have become more and more widespread, and switches have played an important role as a link in the network. increasingly important role. Simply put, the switch just connects it to the user's computer to complete the data exchange between the computers. To put it more complicated, in terms of the position of the switch in the entire network, some high-level switches, such as three-layer switching and network-managed products, are not so simple in terms of switch structure.
Three-layer switch
Usually, ordinary switches only work on the data link layer, while routers work on the network layer. The powerful three-layer switch can work at the data link layer and network layer at the same time, and forward data packets based on the MAC address or IP address. However, it should be noted that the three-layer switch cannot completely replace the router, because it is mainly used to implement VLAN communication in two different subnets, rather than for complex path selection for data transmission.
Network management function
The management level supported by a switch reflects the manageability and operability of the device. Switches with network management functions can monitor the traffic of each port, set the rate of each port, and close/open port connections. By monitoring switch ports, it is easy to distinguish network business traffic and quickly define network faults, improving network manageability.
Port aggregation
This is an encapsulation technology. It is a point-to-point link. Both ends of the link can be switches or Switches and routers, but also hosts and switches or routers. Based on the port aggregation (Trunk) function, it allows parallel connections between switches and switches, switches and routers, hosts and switches or routers through two or more ports for simultaneous transmission to provide higher bandwidth and greater throughput, significantly providing the entire Network capabilities.
For more related knowledge, please visit theFAQcolumn!
The above is the detailed content of What are the operations included in the working principle of a switch?. For more information, please follow other related articles on the PHP Chinese website!