How to learn computer networks? Computer network and network security

Problem:
I always feel that the network is complicated, and I have not studied the network principles carefully before. If I can talk about some cases, it would be nice to have a DIY experiment on the computer?

--------------------------- 0x00 Basic Introduction: Basic Concepts ------------------------------

Generally speaking, network knowledge refers to computer network knowledge. In general, network knowledge is indeed relatively broad.
Especially when I first started learning, I found that there were a lot of things to learn, the general learning process starts from the layer-5 protocol stack (physical layer, data link layer, network layer, transmission layer, and application layer) of TCP/IP. The layer-5 protocol stack can be seen as a global generalization of network knowledge. You need to know the protocols related to the layer-5 protocol stack (the physical layer can generally be ignored, for example, the data link layer has the ARP protocol, the network layer has the IP protocol, and the transmission layer has the TCP/UDP protocol, many application-layer protocols, such as QQ-related protocols.

Further study may involve knowledge about routers and VPNs. There are many different types of vro protocols, such as BGP, RIP, and OSPF. Don't be scared by these Protocols. You don't need to remember the details of the Protocols, as long as you know the approximate functions of each protocol and the differences with other protocols, you can check the manual or google as needed.

------------------ 0x01: Several scenarios of learning computer networks during operations ----------------------

1. The simplest computer network configuration should be to configure the IP address, gateway, subnet mask, and DNS of your computer when accessing the internet in the lab. For example, set the local IP address of win7

What can I learn from the above operations?

* Knowledge point: you can understand the concepts of IP, gateway, and subnet mask. You can try to modify some parameters and see the impact on the Internet. As mentioned above, setting DNS allows you to find related knowledge about DNS (what is it + What can it do)

2. The lab engineer asked me to connect my new server to the Internet. However, the lab's existing network cable is too short and the server is too far away from the plug-in. What should I do if I need to connect the server to the crystal head on the network cable? Cable connector

* Knowledge point: why is the network cable eight lines? When was the current network cable invented? What are the performance advantages of the current network cable?

3. My beautiful neighbor bought a new router and asked me to install it. What should I do? For example, how to configure a router?

* Knowledge point: what is a vro and how it works? What are the dial-up methods for Routers? What are the security configurations of routers? What are the differences between WEP, WPA, and WPA2 in encryption mode? What is service quality and congestion control?

4. after a route entry is installed in the dormitory, some people download large movies during the game, which is cut down for three seconds. I want to control him to access the Internet, is there a more rational way to remove his power and force the shutdown? Click here to download the required artifacts.

* Knowledge point: why can network scissors control others' Internet access? If I am hacked and my network scissors are disconnected, is there any more rational solution besides being in the middle? So I need to learn about ARP spoofing, ARP spoofing-wiki, ARP spoofing-Baidu encyclopedia

5. recently, I am idle. I am working part-time in the network center. I have a job opportunity to get the network access traffic at the school's entrances and exits. I want to see if everyone is online, what are your favorite websites? What are the keywords frequently used for Google and baidu searches?

* Knowledge point: if you want to parse network traffic, you should at least know the common traffic packet format. For example, HTTP traffic is generally used for the destination port 80, statistics on the proportion of HTTP traffic can tell you how long it takes to browse the Web page. Obtain the websites accessed from the HTTP traffic, and then make a statistical analysis to obtain the top 10 frequently used websites. Analyze the traffic used to access Baidu and google separately to obtain common keyword information.

6. I forgot to pay the Internet fee at the beginning of the month, but now I need to urgently send a file to BOSS. But I know that Tom is playing online games all night, at the last dinner, he heard GF say that his memory was poor. Therefore, James set a simple password. Can I get rid of the Internet ??? Aircrack-ng tutorial

Network security to understand computer networks. Several keywords: Protocol Vulnerability Analysis, route spoofing, DNS pollution, man-in-the-middle attack, and GFW.