Three Musketeers of hardware known as network hubs (Hub), switches (Switch) and routers (Router) network has been the activist community, but so many doors entering the network of rookie angry is that they not only look like three, and often stay together, in order to distinguish who is who, feeling somewhat difficult. We take a look at the differences and connections between them.
First, the hub
Prior knowledge hub, we must first look at the repeater. We come into contact with the network, the simplest is two computers configured by the two card "duplex interconnection", it is generally made to act as unshielded twisted pair of signal lines between two network cards. Since the signal power is gradually twisted in the transmission signal is attenuated, when the signal is attenuated to a certain extent will cause signal distortion, and therefore the premise of ensuring the quality of the signal, the maximum transmission distance of 100 meters of twisted pair. When the distance between the two computers over 100 m, in order to achieve double interconnection, people between the two computers installed a "repeater", its role is to have a signal attenuation is not complete after organize, complete signal regeneration to continue the transfer.
Repeater hub is common predecessor, the hub is in fact a multi-port repeater. 4,8,16,24,32 hubs generally have an equal number of RJ45 interface, through these interfaces, the hub be able to complete a "relay" function to the appropriate number of computers. Since it is in a "central" position in the network, and therefore the hub also called "the Hub."
Second, the switch
Switch also called a switching hub, it is regenerated by the information, and forwarded to the specified port, after internal processing, and includes automatic addressing capability exchange interaction, since the switch according to the destination address of the transmitted packet, each packet will independently from the source port to the destination port, and other ports to avoid the collision. Generalized switch device is a kind of complete information exchange function in a communication system.
If the hub compared to a postman, then this is a postman do not know the word "fool" - messenger to him, he did not know the address on a letter directly to the letter sent to the recipient, only took the letter distributed to all people, then let the person receiving the information to determine the address is not your own and switch is a "smart" postman -! switch back has a high bandwidth internal bus and switch fabric. All ports of the switch mounted on the back of this bus, When the control circuit receives the packet, the process looks port memory address table to determine the purpose of MAC (NIC hardware address) of the NIC (network card) linked connected to which port, quickly transferred through the internal switching matrix data packet to the destination port. Destination MAC if not, switch it broadcast to all ports, the switch will respond after receiving the port "learn" the new address, and add it into the internal address table.
If you use the most simple language to describe the difference between switches and hubs, they should be the difference between intelligence and non-intelligence. White said hub network device connecting a plurality of computers only, it can only function as signal amplification and transmission, the signal can not be processed in fragments, so prone to error during transmission. And the switch may be regarded as an intelligent hub, in addition to all the features that it has a hub, and also has an automatic addressing, switching, the processing function. And the data transmission process, the transmission side and reception side work independently, relations with other ports, so the purpose of improving the throughput of data loss and achieve the prevention.
Third, the router
Through a hub or switch, we can be a lot of computers to form a relatively large LAN, but when the number of machines up to a certain number of problems will come: For a local area network consisting of a hub, since the use of "broadcast" mode of operation when large-scale network, message appears during transmission collision, clogging more serious, even the switch, this situation also exists. Second, this LAN unsafe, is not conducive to management.
To solve these problems, people put a larger network into subnetworks of a small, segment, or direct them to divide into multiple VLAN (virtual local area network that is), in a VLAN, a host issued can only be sent to another host with the same VLAN number, other members of the VLAN do not receive the information or broadcast frame. With division VLAN network, the broadcast storm can be effectively suppressed on the network, increasing the security of the network, making centralized management control.
Since it is a local area network, respectively, in the case of how to do different VLAN hosts need to communicate with each other? This time you have to help through the router (Router, forwarder) a. Routers can be in different subnets network segment, VLAN computers connected so that they communicate freely. In addition, we all know that the current network structure there are many types and protocols used by different networks, and speed are not the same. When the network needs to interconnect two different structures, may be realized by a router. Router enables two similar or different architectures LAN segments connected together to form a larger LAN or a WAN.
Visible, a router or the network segment connected to a plurality of network devices, capable of data information between the different networks, VLAN segments or a "translation" to enable them to each other "read" understand each other's data, so as to constitute a larger network.