The classic article is very good for the newcomers. It is a vivid and lively and easy to understand. It is the article used to get started. From time to time. I just found it in my own collection document, since I have blog, I simply sort out.
Let the Fox Road entered Huashan in the middle of the year, then Yue Lingshan eight years old, Yue Yue brought two people to the two priests during the day, and the night made Fox to the young teacher. She fell asleep.
Later, Yue Yue had repeatedly received Laudno, Lu Da has some apprentices, and he was busy practicing Zi Xia Meng, there was no time to point to apprentice. So he made a HUB. From then on, Huashan sent e-year, Yue Yue gave each apprentice to each apprentice online, this method quickly promoted within Wuyue Sword. In order to interconnect between the Wuyue Sword, the Lushanpai head has developed the router, so that the five-bedroom swords can interconnect. Let the foxhrie have given a story from the brother girl through the Internet.
Soon, Yue Lingshan has been sixteen years old and has become a slim little girl. Linghu Chong found that his gaze always stopped on the child's girl, every time with the Xiaoshi, I always hear my strong heartbeat, after a period of tea, I finally had one night, Linghu rushed on the Internet to give the Major Sister a feeling of affection:
You are a wind, I am sand, you are a bee, I am a flower, you are a comb, I am a hair, you are a toothpaste, I am a toothbrush.
The next day, Huashan School was opened, and the mood of Fox fell to the conference room, and found that the teacher's red face was hiding behind Master, and other brothers were secretly laughing at themselves, once, one The brother of the naughty brother is called the toothbrush, and quickly escaped. Asked Lu Da, I know that Laudno uses a tool called Netxray to take her online masterpiece.
Let the fox have revived a lot, so closed the door to study RFC, successfully developed Lanswitch (Ethernet switch). It can identify the device MAC address so that the data that makes the fox buning to the small teacher is only a person can receive. Let the foxhoke you can tell the story at the end of the net, and occasionally itch can knock a few words, you will be able to say anything else. Then, the red face is imagined to see the expression after the young teacher.
Lanswitch is a Layer 2 switching device that understands the Layer 2 network protocol address MAC address. The two-layer switch constantly collects the information in the operation to build its own address table, which is quite simple, mainly indicating which port is discovered on which port is discovered, so when the switch receives a data package, it The destination MAC address of the package will be checked, check the address table to determine which port is sent. Not like Hub, any hairper data will appear on all ports of HUB (regardless of whether you need it). In this way, Lanswitch also improves system security while increasing efficiency.
The next year, Yue did not enroll a lot of disciples, Huashan sent a large growth, and the Lanswitch used also many times. However, the disciples were inexplicably mixed. At that time, Huashan sent a group of three. The four generations of disciples worship Miles Octagon, set up a field of field, often broadcasting eight hundred meters or more than one thousand meters; there is a question; one of the third generation disciples Call Li Hong, every day, in the Huashan Pie, the Broadcasting Radio Dafa; more let the fox can't be affected, with the increase of Master's age, it becomes more and more, each sentence must be repeated twenty times. Then broadcast online.
Linghu Zhi and Xiaosi, Lu Da has some people to use a broadcast domain, but if you use a lanswitch, Master will definitely not agree, so he has modified the Software of Lanswitch, put the little teacher, Lu Da, etc. It is divided into a virtual network (VLAN), and others use additional VLANs, and the broadcast package is only transmitted within the VLAN, and the VLAN is connected to the router. Yue Yue also suffered from Tianx Association, Li Hong to his harm, but in order to fight with left cold, the use of people, only tolerance, knowing this, is very happy, but still makes the fox privately modify the software, Filled him to think about the wall of the cliff, not to go down within a year. In the Huashan Palace re-use VLAN to divide the subnet, divided into five subnets, Master and Teachers, Xiaoshi and Lin Ping in a VLAN, round the disciple with a VLAN; the field disciples use a VLAN, other disciples With a VLAN, there is a separate VLAN on the cliff. Linghu rushed to the cliff, it was not difficult, finally, the world is quiet, relying on the router of the left and cold Zen, letting the fox fortune can tell the young master girl online every day, chat.
The introduction of the LAN switches allows the network nodes to have alone, but for the second-layer broadcast packet, the Layer 2 switch is broadcast on each network node; at the same time, the MAC address that cannot be identified for the Layer 2 switch must also be Broadcast domain is broadcast. When multiple Layer 2 switch levels, all devices on the Layer 2 switching network receive broadcast messages. In a large two-layer broadcast area, a large number of broadcasts greatly reduce the efficiency of the second layer forwarding, in order to avoid the broadcast storm caused by broadcasts on large switches, it is necessary to further divide multiple virtual in a two-layer switching network. Net (VLAN). In a virtual network (VLAN), information issued by a workstation can only be sent to other sites having the same virtual network number (VLANID), and the other virtual network (VLAN) can not receive this information or broadcast frame. The virtual network (VLAN) can control the broadcast storm on the network and increase the security of the network. Communication between Different Virtual Network (VLANs) must be performed via a router.
But happiness is always short, and it is always endless troubles. With the increase of the entire five-bedroom sword, the speed of the router is getting slower. Linghu Chong finds that every time I tell the story, the answer of the young teacher is always in Shanshan, and there is very little words, always "hmm", "" or "I listen". Finally, one day, the router is no longer ping, so that the fox rushed three days without the news, facing the empty display, I couldn't help, on a snow, secretly down the mountain to find a young teacher, to the small teacher In front of the window, I found that the teacher is chatting online and the small forests. I didn't pay attention to myself, my heart sore, I went back to the cliff, a big disease. After the disease is good, I finally study, and finally one day, made a router.
At this time, the Fox Chong found that the Huashan School has thirty VLANs, and the router must allocate an interface for each VLAN. The interface is not enough, and the switching speed of the router through the router is much lower than the second floor exchange through the router. speed. After the Layer 2 switch divides the virtual subnet, there is a problem: the forwarding between different virtual subnets need to be implemented by other routers.
Different VLAN nodes between the Layer 2 switch need to be greatly wasted through the router device, while the high cost of the router makes it unable to meet the three-layer forwarding demand, three-layer exchange concept in the case of large quantities. Just in this case it was mentioned. This evening, letting Fox embrace, borrowing alcohol, at this time, a black shadow appeared in front of him, it was an old man with a rumor, it was a wind. Feng Qing listened to the doubts of Fox, said: The router interface is not enough, and the router can not be used inside the lanswitch; the switching speed is slow, because the router looks for network segment routing, and Lanswitch directly check the port, of course high speed. Why can't I find out the port directly according to IP addresses? Let Fox Chong listen, it is very admired, but still does not understand, the IP address is so much, and often changes, how can I directly find the port?
Feng Qingyang said: "You first sit down, let me ask you, how many disciples have Huashan send?" "" "" "Do you know where they live?" "I don't know." "Yue does not Group wants you to find someone who doesn't know where to live, how to find it? "" Tracing Huishan School phone number query system, find his address, then find him. "" If you come back, let you find this person, and How to find it? "" How to .... Tracing Huashan School phone number query system, find his address, then go to him. "" Don't you know the address of this person? "" Know, Master said, The address of Huashan School is so much, and often changes, don't know how to address. "" Yue Yue, this child, teaching the apprentices into wood! I ask you, what do you think should be? "" Go directly! "" Ok! You are still too benzene. After you know the address of a person, is it always remembered? "Some people remember. Other forgot." "Why for forgotten?" "Because I can't remember so many people, and I didn't find him for a while." "How is the address in the Huashan phone number query system?" "I shouted his name in the air, he heard Just come to me, tell me his address. "Feng Qingyang asked the problem with brain tendons, then the wind cleared:" Now you understand the truth of the port directly according to the IP address? Wait until you understand this truth, you will naturally make a three-layer switch. "
Let the Fox Chong carefully recalled today, and finally understood the truth of the two-layer forwarding from the MAC address corresponding to the port. The three-layer forwarding can also directly correspond to the port, the route of the IP address can be learned by ARP, the same Need aging. Thus, the VLAN is forwarded in addition to the first package to get the host route through the ARP, and the other packets can find an outlet directly according to the IP address, and the forwarding speed is much higher than the speed of the router forward. When looking up, the wind cleared.
One year later, the Fox was so thinking about the cliff, successfully launched the QuidWays8016 routing switch. The interoperability between VLANs is realized, and interoperability is achieved with routers such as Lushan, Blackwood Cliff. The three-layer switch is to increase the three-layer switching function on the basis of a Layer 2 switch, but it is not a simple Layer 2 switch plus router, two but uses different forwarding mechanisms. The forwarding of the router uses the longest matching method to achieve complicated, usually using software to implement,. The routing of the three-layer switch is a steady stream. It uses Cache technology, it is easy to use ASIC implementation, so it can be greatly saved and fast forwarding. Many articles will mention the difference between the three-layer switches and routers, the general comparison is the three-layer switch and cheap. These words are not wrong, but the occasion is a gathering layer. We see, in the aggregation layer, the host directly hanging directly, because the host routing can be obtained, so the three-layer switch can realize fast lookup; for the host, three layers arriving after connecting multiple subnets through other routers The handling of the switch and router is the same, and the maximum matching method is used to find the next hop, and the next hop router is forwarded. Therefore, the usual networking method is to use GSR in the backbone layer, and the aggregation layer uses a three-layer switch. Of course, for a small metropolitan area, you can directly take the three-layer switch network, do not need GSR. Next goal: improve English speaking and listening, then find a good job, then learn ATM, VPN, MPLS, OSPF, BGP4 ..., there is also C , Linux, SQL ... ... Waiting for a few years of work experience to take the NP.
