【 Weak current college 】 teaches you a full understanding of bridging, switching and routing---Power By 【 China power house network 】

I just contact network knowledge, sometimes a always will be one of the problems, that is, bridging, switching and routing differences between, most beginners computer network knowledge of Internet users have such friends.　　The other day that met an old friend friends ask such questions, today I will take you to understand what is bridging, switching and routing, and the differences between the three scenarios and for a detailed introduction.　　1. What is a bridge bridge work in OSI network reference model of second-tier data link layer, is a MAC address as a judgment pursuant to the network is divided into two distinct physical segments of technology, it is widely used in the early computer network.　　We all know that Ethernet is a shared network of technology, the transmission medium in this technology, if a computer sends data, on the same physical computer on the network media requires receiving, after analysis of the purpose of receiving a MAC address, if you belong to the destination MAC address and your Mac address is the same as that for package available to the network layer, if the destination MAC address is not your own MAC address, it will drop the packet. Bridging works is the physical network segment (also is often say collision domain) separated, according to the MAC address to connect two physical network segment of the computer sending the packet.　　Below, we give an example to explain for netizens: in the following illustration of the network structure, two hub connected to multiple computers, we are A hub and hub for B A collision domain and domain B conflicts.　　In such a network environment, if computer A to computer C send packets, hub A packets across the network of all of the computers (including hub B) send it again, regardless of whether the packet is not necessary to send to another region B. We then A hub and hub b connected to bridge two ports, if computer A to computer C sending packets will experience what? when the hub is equally A packets sent throughout the network, when you reach the bridge, the bridge will be packet destination MAC address analysis and comparison of their learning to the MAC address table, if the table does not have this MAC address, network bridge is in two segments on the send packet, while the computer is A MAC address record in your table.　　After many such records, the bridge will include all of the MAC address of record, and divided into two segments. When computer A sends a packet to B again, because the two computers with a physical card cost, packet arrives on the bridge, the bridge will end MAC address, and your own tables for comparison and judgment computer A and computer B in the same segment, will not be forwarded to region B, but if you are not in the same physical network segment, will allow packets to pass through a bridge.　　The above example we understand that the bridge is actually a control device conflict domain traffic.　　The bridge now basically have rarely used, isolates the collision domain, network bridge can also implement different types of network connection O (token ring and Ethernet connections) and network expansion (IEEE 5.4.3 connection rules), and so on.　　2. What is a swap-Exchange also work in the OSI reference model for the network's second-tier data link layer, is also a way to MAC address as a judgment pursuant to the network is divided into two distinct pieces of technology, except that the Exchange be physical network segment is divided into each port, the simple understanding that is a multiple port Ethernet bridge, it actually is a bridging technology. In the previous understanding, we already know the bridge that connects two different physical network segments (collision domain) technology, the Exchange is to connect more than one physical network segment technology, typical switch normally has multiple ports, every port is a network bridge, when connected to the switch port of the computer you want to send a packet, all ports willdetermine whether the packet is sent to your own, if not just dropped, this collision domain concepts to each switch port. We for example to explain, in the following figure, we can see the computer A and B are connected to different ports of the switch, when computer A sends a packet to b, it is assumed that when A port is not learning to b port MAC address, A port will use broadcast packets sent to A port other than port (broadcast domain), while other computer receives the packet will be and your own MAC address, then simply discard the packet;　　B receives the packet, the packet through comparison, after receiving and recording source address. By repeated such learning, switch will construct a forwarding based on all ports, the database is stored in the content addressable storage switch among them (CAM).　　In the switch to all ports, computer A sends a packet to B again, is no longer a broadcast address, but sent directly to the forwarding database corresponding B port. Through this learning, switch on the micro-segments, each connected to switch ports that computers can be dedicated bandwidth. 3. What is routing routing work of the OSI reference model of the third layer of the network layer, it is based on the third floor of the IP address information as a criterion to be network divided into different segments (IP subnet) technology, and bridging and switching, routing group is an independent logical segments, each of the connected network segments are independent of the network IP address information, rather than the MAC address as the basis for judging the path so that routing will have the ability to isolate broadcasting;　　and the Exchange and bridging is divided into physical network segment, they merely physical transmission media segments. While routing functionality with path selection, depending on the destination IP address of the destination most appropriate path. We see the router is connected to the three switches, the three switches were divided into three different subnet addresses: 192.168.0.0, 192.168.1.0, 192.168.3.0.　　When computer A to theB send packets, do not know the path to reach the B, switch A packets in their own segment on full network broadcast, when you reach the router, the router will not be broadcasting this packet, it rules under a routing protocol to judge arrived B should select forward it to the segment, then the packet is forwarded to the corresponding IP address section, and not to broadcast to not need this package C segment. If the router does not have a rule definition arrived at the destination IP address of the path, it will drop the packet. Routers are the choice and data forwarded two basic functions, but in many scenarios, the router is generally has a gateway that role.　　At home, we usually use PPPOE dial-up or static routes both for LAN shared Internet access.　　In this case, the router's main function is to achieve LAN and Wan of protocol conversion, this also is the main purpose of the gateway.　　IV. the distinction between 1, located in the reference model layer different in the open systems interconnection reference model, bridges and switches are located in the reference model in the second level-data link layer, while the router is located on the higher level-the network layer.　　2, based on the judging criteria of path is different because is located in the OSI reference model layer, so that the switches, gateways, the two devices to determine the path of conditions vary, bridges and switches by port's MAC address to determine packet forwarding, and router IP address is used to judge.　　3, the ability to control the broadcast different bridges and switches (three-layer switches or support VLAN features excluded) for both devices will be unable to control network broadcast, if you have a broadcast packet to all port forwarding, so in a larger network environment, you must have a router to control network broadcast. 4, intelligent degree in judging data, network bridge canonly determine whether on the same physical network segment, the switch you can judge the packets belong to the port, but both devices have the ability to choose the optimal path and router path based on IP address to determine, based on the IP address information to determine the optimal path to the destination.　　Five, three different scenarios and future development in the real application environments, network bridge is basically will not be used in small and medium-sized local area network, the most commonly used networking equipment to which is to switch, you select router based on the size and functionality of the network to determine, in a large network, the router is to be used to control the radio, but because the technology continues to extend, the switch is integrated with the path based on the IP address to determine and control the broadcast function, so the router now progressively be routable-switch. The previously mentioned, the router in many scenes are been used gateway, so that with the rapid development of broadband technology, in the last kilometers, a new device-broadband router will gradually replace the traditional router to implement network access feature. I believe that through the introduction, above all for the network bridge, switching, routing and gateway functionality with a clearer understanding!