What are intra-network, inter-network and point-to-point text messages?

To put it simply, there is a local area network within our work unit, home, or community; outside our work unit or home, there is a network with a wide coverage, such as the Internet. This large network extends to our work unit and home (through Optical fiber, network cable, telephone line, etc.). When we connect our LAN to the Internet, our access scope extends from the LAN to the entire Internet. At this time, it is said that the LAN is the internal network and the internet is the external network.

Similarly, if your unit's LAN is very large, and a small LAN composed of several computers in your office is connected to the entire unit's large LAN, then it can also be said that the unit's large LAN is an external network. Network, the small LAN in the office is the intranet. At the same time, if the unit's large LAN is connected to the Internet, then compared to the Internet, it can also be said that the unit's large LAN is an intranet.

The intranet may be an independent LAN, through its gateway (a gateway is a node that connects two networks. To put it bluntly, it is a computer with dual identities, both the IP address of the LAN and the Internet IP address, two IP addresses are bundled on different network cards) proxy access to external networks, such as Internet cafes are implemented in this way, its characteristics are: the IPs of the computers in the Internet cafe are all LAN dedicated IPs, such as 192.168.xxx .xxx or 10.xxx.xxx.xxx, and this kind of IP will not appear on the Internet.

(Note: The so-called agent means that when you make a request, he will handle the matter, which is similar to purchasing train tickets. If a computer in the LAN wants to communicate with the outside world, it tells the server, that is, the gateway, the address of the other party. The gateway uses its own Contact the other party with your own identity and forward the message sent back to the computer in the LAN. Therefore, the other party cannot see the IP of the computer in the LAN and will only think that the computer at the gateway is communicating with itself. The same IP is displayed, can you understand why now? )

The internal network may also be a part of the external network, such as the campus network, or the office internal LAN relative to the unit LAN. Its characteristics are: the IP of the internal network computer is part of the entire external network IP range. The internal network computer is connected to the external network through the gateway (router). The gateway does not need to provide proxy services, just route directly.

(Note: The so-called routing refers to path selection. The router connects multiple networks, so it must be the gateway of each network. Its function is similar to the post office. If you want to contact a computer outside the LAN, send the mail package to The router will help you deliver the package to the address marked on it. In this way, the person who receives the package can know who sent the package, but he cannot know whether the person who sent the package is sending the package on behalf of others. That is, the computer that receives the data can know which computer is contacting it, but it cannot know whether the computer it is contacting is a proxy server of a certain local area network)

adsl is special. It works in two ways. The first one is that adsl's modem turns on the proxy function. At this time, the modem can actually be regarded as a computer. It is a node of the Internet (external network). At the same time, it is connected to your computer to form a local area network, that is, the internal network. Network, the intranet gateway is the modem. The second type is dial-up Internet access through a computer. In this case, the modem is an external device of the computer, and your computer is directly connected to the Internet through a phone line. There are no other networks, so there is no internal or external network.