Differences and connections between switches, routers, hubs, network cards and other network equipment
Network card and router are two kinds of network hardware devices. The network card is the interface device between the network terminal and the network; the router is used to guide the information transmission in the network.
Hub Hub is actually a multi-port repeater. The hub generally has 4, 8, 16, 24, 32, etc. RJ45 interfaces. Through these interfaces, the hub can complete the "relay" function for the corresponding number of computers (the signals that have been attenuated incompletely are sorted out and regenerated Continue to send a complete signal). Because it is in a "center" position in the network, the hub is also called "Hub".
The working principle of the hub is very simple, for example, there is a hub with 8 ports, a total of 8 computers are connected. The hub is at the "center" of the network, and the signal is forwarded through the hub, and 8 computers can be interconnected. The specific communication process is this: If computer 1 sends a message to computer 8, when the network card of computer 1 sends the information to the hub through the twisted pair, the hub will not directly send the information to computer 8, it will "Broadcast" the information-send the information to 8 ports at the same time, when the computer on 8 ports receives this broadcast information, it will check the information, if it is found that the information is sent to itself, then receive , Otherwise ignore it. Since the information was sent by the computer 1 to the computer 8, the computer 8 will eventually receive the information, and after reading the information, the other seven computers will not receive the information because the information is not theirs.
The switch is also called a switching hub. It regenerates the information and forwards it to the designated port after internal processing. It has automatic addressing capability and switching function. Because the switch divides each message according to the destination address of the transmitted packet Packets are sent independently from the source port to the destination port to avoid collisions with other ports. A generalized exchange is a device that completes the information exchange function in a communication system.
In the computer network system, the switch is introduced for the weakness of the shared working mode. The hub is a representative of the shared working mode. If the hub is compared to a postman, then the postman is a "fool" who does not know the word-asking him to send the letter, he does not know to send the letter directly to the recipient based on the address on the letter , Will only distribute the letter to all people, and then let the recipients judge whether they are their own according to the address information! And the switch is a "smart" postman-the switch has a high-bandwidth back bus and internal switching matrix . All ports of the switch are connected to this back bus. When the control circuit receives the data packet, the processing port will look up the address comparison table in the memory to determine the destination MAC (hardware address of the network card) and the NIC (network card). Connected to which port, the data packet is quickly transferred to the destination port through the internal switching matrix. If the destination MAC does not exist, the switch broadcasts to all ports. After receiving the port response, the switch will "learn" the new address and add it to the internal address table.
It can be seen that when the switch receives a "letter" from a certain network card, it will quickly send the letter to the recipient according to the above address information and the "resident booklet" held by the switch. In case the recipient's address is not in the "hukou", the switch will distribute the letter to all people like a hub, and then find the recipient from it. When the recipient is found, the exchange will immediately register the person's information in the "Account Book", so that when the customer is served later, the letter can be quickly delivered.
Router A router is a key device for interconnection in a network. As a hub for interconnection between different networks, the router system constitutes the main thread of the international interconnection network Internet based on TCP / IP.
The router is in a key position in the interconnected network because it is at the network layer. On the one hand, it can span different physical network types (DDN, FDDI, Ethernet, etc.), and on the other hand, it logically connects the entire interconnected network. Divided into logically independent network units, the network has a certain logical structure. The main job of the router is to find an optimal transmission path for each data frame passing through the router, and effectively transmit the data to the destination site.
The basic function of a router is to transmit data (IP packets) to the correct network. The breakdown includes: 1. Forwarding of IP datagrams, including routing and transmission of datagrams; 2. Subnet isolation to suppress broadcast storms 3. Maintain routing tables and exchange routing information with other routers, which is the basis for IP packet forwarding; 4. Error handling and simple congestion control of IP datagrams; 5. Implement filtering and accounting of IP datagrams .
The router constitutes the skeleton of the Internet. Its processing speed is one of the main bottlenecks of network communication, and its reliability directly affects the quality of network interconnection. Therefore, in the field of Internet research, router technology has always been at the core.
Recently, I have seen many people asking what switches, hubs, and routers are, how they function, and what is the difference. The author simply answers these questions.
Let me talk about HUB first, which is the hub. Its role can be simply understood as connecting some machines to form a local area network. The switch (also known as a switching hub) is basically the same as a hub. However, there is a difference in performance between the two: the hub uses a shared bandwidth working method, and the switch is exclusive to the bandwidth. In this way, when there are many machines or a large amount of data, the two will be more obvious. The router is obviously different from the above two. Its role is to connect different network segments and find the most suitable path for data transmission in the network. It can be said that individual users generally have little demand. The router is generated after the switch, just like the switch is generated after the hub, so the router and the switch also have a certain connection, not two completely independent devices. The router mainly overcomes the deficiency that the switch cannot route and forward data packets.
In general, the main differences between routers and switches are reflected in the following aspects:
(1) Different working levels
The original switch was working at the data link layer of the OSI / RM open architecture, which is the second layer, and the router was designed to work at the network layer of the OSI model from the beginning. Since the switch works at the second layer (data link layer) of OSI, its working principle is relatively simple, while the router works at the third layer (network layer) of OSI, can get more protocol information, the router can Smarter forwarding decisions.
(2) Different objects based on data forwarding
The switch uses the physical address or MAC address to determine the destination address for forwarding data. The router uses the ID numbers (ie, IP addresses) of different networks to determine the data forwarding address. IP addresses are implemented in software and describe the network where the device is located. Sometimes these third layer addresses are also called protocol addresses or network addresses. The MAC address is usually carried by the hardware, and is assigned by the network card manufacturer, and has been solidified into the network card, and generally cannot be changed. The IP address is usually automatically assigned by the network administrator or system.
(3) Traditional switches can only divide conflict domains, not broadcast domains; routers can divide broadcast domains
The network segments connected by the switch still belong to the same broadcast domain, and broadcast packets will be propagated on all network segments connected by the switch, which in some cases may cause communication congestion and security holes. The network segments connected to the router will be allocated into different broadcast domains, and the broadcast data will not pass through the router. Although switches above the third layer have the VLAN function and can also divide the broadcast domain, the communication between the sub-broadcast domains is not possible, and the communication between them still requires a router.
(4) The router provides firewall services
The router only forwards data packets at a specific address, and does not transmit data packets that do not support routing protocols or unknown target network packets, thereby preventing broadcast storms.
The switch is generally used for LAN-WAN connection. The switch belongs to the bridge and is a device at the data link layer. Some switches can also implement the third layer of switching. The router is used for WAN-WAN connection, which can solve the forwarding of packets between heterosexual networks, acting on the network layer. They just accept incoming packets from one line and forward them to another line. These two lines may belong to different networks and use different protocols. In comparison, routers are more powerful than switches, but they are relatively slow and expensive. Layer 3 switches have both the wire-speed forwarding capability of switches and the router's good control functions, so they are widely used.
At present, more personal broadband access methods are ADSL, so I will briefly explain the ADSL access. Most of the ADSL cats that are purchased now have routing functions (many times the manufacturer shields the routing function at the factory, because most of the telecommunications installation does not enable the routing function, enable DHCP. Turn on the ADSL routing function) A few can be used by ADSL itself, if you have more computers, you only need to buy one or more hubs or switches. Considering that the price difference between the hub and the switch is very small today, it is not a special reason, please buy a switch. There is no need to pursue high prices, because the homogenization of products is very serious now, and my cheapest switch now has no problems. Give you a reference quotation, it is recommended that you buy an 8-port to meet the expansion needs, the general price is about 100 yuan. Connect the switch, and then connect all the computers to the switch. The only thing left to do is to insert the network cable of each machine into the interface of the switch and the cat's network cable into the uplink interface. Then set the routing function, DHCP, etc., you can share the Internet.
After reading the above explanation, readers should have some understanding of switches, hubs, and routers. The current use is mainly based on the combination of switches and routers. The specific combination can be determined according to the specific network conditions and needs.
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