The IP address and the MAC address are paired. The switch works at the second layer of the data link layer. Generally, the data frame is forwarded by the MAC address field in the received data frame. The data frame includes a frame header and a data portion. End of frame.
Ethernet is the most common communication protocol standard used in existing LANs. Ethernet uses CSMA/CD (Carrier Sense Multiple Access and Collision Detection) technology and runs on multiple types of cables at 10M/S. From the development process of the medium, it has experienced coaxial cable, unshielded twisted pair, and fiber.
The repeater works at the physical layer. The main function is to increase the distance of network transmission by resending or forwarding data signals.
A hub, known as a multiport repeater, is a device that connects multiple Ethernet twisted pairs or sets of fibers together on the same physical medium. The node sends a signal to the line, and the hub receives the signal for amplification and broadcasts it to other ports.
MAC: Physical address used to define the location of a network device.
48, the first 24 codes assigned by the Electrical and Electronic Engineering Association to different manufacturers, the last 24 are the adapter interfaces assigned by the manufacturer to the production. The MAC address corresponds to the second layer of data link layer of the OSI reference model.
The 8th bit of the first byte of the MAC address identifies whether the address is a multicast address or a unicast address. A MAC address of all 1 is a broadcast address. A switch operating at the data link layer maintains a database of computer MAC addresses and its own ports.
Talking about the MAC address, I have to talk about the IP address. The IP address works in the third layer of the OSI reference model. The division of labor between the two is clear, tacit cooperation, and complete the communication process. The IP address focuses on the network layer and forwards packets from one network to another; the MAC address focuses on the data link layer, transferring one data frame from one node to another node on the same link.
In a stable network, IP addresses and MAC addresses appear in pairs. If a computer wants to communicate with another computer on the network, then configure the IP addresses of the two computers. The MAC address is set when the network card is shipped from the factory. The configured IP address forms a correspondence with the MAC address. . In data communication, the IP address is responsible for representing the network layer address of the computer, the network layer device (such as a router) operates according to the IP address; the MAC address is responsible for representing the data link layer address of the computer, and the data link layer device (such as a switch) Operate according to the MAC address. The mapping relationship between the IP address and the MAC address is performed by the ARP (Address Resolvuation Protocol) protocol.
After the HUB, the switch appears. The switch works at the second layer of the data link layer, also called the Layer 2 switch. The Layer 2 switch forwards the data frame according to the MAC address field in the received data frame.
The so-called data frame is the protocol data unit of the data link layer. It consists of three parts: the frame header, the data part, and the end of the frame.
The frame header of the MAC frame includes three fields. The first two fields are a 6-byte long destination address field and a source address field, the destination address field contains destination MAC address information, and the source address field contains source MAC address information. The third field is a 2-byte type field, and the information contained therein is used to indicate what protocol is used by the upper layer, so that the receiving end hands over the data portion of the received MAC frame to the upper layer.
There are broadcast storms on the Layer 2 switch. For example, if there are multiple departments on the current network, all the departments will receive the broadcast packets when the hosts in one department send broadcast packets. If you want to allow only the current department to receive the packets, you need to use them. To vlan technology (dividing into multiple different broadcast domains). By default these different broadcast domains are isolated from each other. To communicate between different broadcast domains, you need to pass one or more routers. Such a broadcast domain is called a VLAN. It adds a VLAN header to the Ethernet frame. The most widely used VLAN protocol standard is IEEE 802.1Q, which uses VLAN ID to classify users into smaller workgroups, limiting user access between different workgroups. Each workgroup is a virtual local area network. The benefit of virtual local area networks is that they can limit the broadcast range and form virtual workgroups to dynamically manage the network.
The port type is classified according to whether the device connected to the port supports the 802.1q standard. The support is trunk. If it is not supported, it is the access port.
Access: Mainly used to access terminal devices.
Trunk: Mainly used to connect other switches to carry multiple vlans on the line.
The data frame output from the trunk port maintains the vlan ID, and the vlan id is stripped from the data frame output by the access, and then forwarded through the mac address of the switch, thus realizing the virtual local area network.
If you want to communicate between different vlans: you need to use a router. By one-arm, one-arm routing (router-on-a-sTIck) refers to configuring a sub-interface (or "logical interface" on one interface of the router. There is no real physical interface), which realizes the interconnection between different VLANs (virtual local area networks) that were originally isolated from each other. Or through a three-layer switch, that is, a switch with routing capabilities. Ordinary routers implement routing and forwarding through cpu and software. The speed of line-speed forwarding of switches is not very good, and Layer 3 switches implement IP routing functions by using hardware switching mechanisms. The optimized routing software improves the efficiency of the routing process. It solves the problem of the speed of traditional router software routing.
(1) Large screen temperature indication with heating indicator light, working status at a glance.
(2) Microcomputer control, heating and insulation automatic control.
(3) The inner liner is made of high-quality steel plate and equipped with a liner protection device, which is anti-corrosion and pressure-resistant and durable.
(4) It has multiple safety protection functions such as leakage protection, anti-dry protection, over-temperature protection, over-pressure protection, and leakage warning.
(5) The insulation layer is foamed with thickened polyurethane, which has good heat preservation effect and saves energy.
(6) It has a wide range of water pressure and large capacity, and can be used for water at the same time.
Solar Pv Water Heater,Solar Water Heater,No Need Electricity Solar Water Heater,Pv Water Heater
Jinan Xinyuhua Energy Technology Co.,Ltd , https://www.xyhenergy.com