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This article mainly analyzes how to analyze the relevant knowledge points of intranet, public network and NAT, the content is detailed and easy to understand, the operation details are reasonable, and has a certain reference value. If you are interested, you might as well follow the editor to have a look, and follow the editor to learn more about "how to analyze intranet, public network and NAT".

When we do weak power monitoring systems, we can't avoid dealing with IP addresses. After installing cameras, NVR, servers and other devices, we need to equip them with IP. Do you know this IP address? Today, let's talk about what is intranet, public network and NAT address translation?

1. Definition of intranet, public network and NAT

The intranet is also called the local area network. In terms of scope, the intranet is a small part of the network, which generally refers to the network formed under a specific environment, such as the network formed by multiple computers in a family, or the large local area network of the school and the company. The IP of the intranet is generally 192.168.1.100192.168.0.100172.16.1.100. These are intranet IP, the intranet can not be directly connected to the external network, relatively closed, but in the intranet can achieve file management, application software sharing, printer sharing and other services.

Home local area network

The external network, also known as the Internet, is a remote network that connects local area networks or metropolitan area network computers in different regions. Usually can span a large physical range, the coverage can be tens of kilometers to thousands of kilometers, it can connect many regions, cities and countries to provide long-distance communication, forming a global Internet network.

NAT, known as address translation technology, was born in the era of shortage of IP addresses. The public network address of traditional IPV4 has been exhausted. Without NAT address translation technology, many devices cannot connect to the Internet. If many people work in the company or surf the Internet at home, the computer will be assigned a 192.168.1.100 private network address. This kind of address is only suitable for communication within the local area network, not out of the external network. It is precisely because of the emergence of NAT technology that intranet addresses can easily access the Internet.

NAT address translation

2. How to connect the internal network and the external network

For the connection between the internal network and the external network, in addition to the support of the router or firewall equipment on the hardware, you also need to configure the IP address of the computer and router and other devices in advance. The IP address is a 32-bit binary value, which is used to mark the address of each computer in the TCP/IP communication protocol. Usually we use dotted decimal system, such as 192.168.1.100. The Internet is made up of many small Lans, and there are many hosts on each network, thus forming a hierarchical structure. In the design of IP address, considering the hierarchical characteristics of address allocation, each IP address is divided into two parts: network number and host number, which facilitates the addressing operation of IP address.

① IP address classification

The IP address can be divided into two parts, the network number and the host number. The network number represents the network segment number to which it belongs, and the host number represents the address number of the host in the network segment. IP addresses can be divided into five categories A, B, C, D and E:

Category A: 0.0.0.0-127.255.255.255

Category B: 128.0.0.0-191.255.255.255

Class C: 192.0.0.0-223.255.255.255

Category D: 224.0.0.0-239.255.255.255

Category E: 240.0.0.0-247.255.255.255

Among them, type A, B and C addresses are called unicast addresses, which are used to identify the interface of a terminal device, while messages whose destination address is a unicast address are called unicast messages; class D addresses are called multicast addresses, and messages whose destination address is a multicast address are called multicast messages. Interfaces with specific functions enabled by some devices can receive multicast messages corresponding to multicast addresses; class E addresses are not available for the time being. There is also a special address 255.255.255.255, called the broadcast address, which can be received by all devices in the local area network.

Among the IP addresses, there are three addresses dedicated to private network planning, which cannot be used for Internet connections as follows:

Category A: 10.0.0.0-10.255.255.255

Category B: 172.16.0.0-172.31.255.255

Class C: 192.168.0.0-192.168.255.255

It is precisely because of the emergence of the private network address that solves the IP problem of the computer terminal equipment in the local area network, but also because of the emergence of NAT technology, the intranet address can easily access the Internet, but the Internet address access to the intranet terminal device is very troublesome, and port mapping is needed if you want to access it.

② Port Mappin

Port mapping means that a port of the IP address of a host in the external network is mapped to a device in the internal network to provide the corresponding service. When the user accesses the IP port, the server automatically maps the request to the terminal device within the corresponding local area network. The port mapping of the configuration is very simple. Enter the router WEB interface to configure the internal network IP address and the mapped port, external port and protocol. After the configuration, the configuration takes effect.

Port forwarding

3. NAT application

The main function of NAT is to configure private IP addresses in the private network, and then convert them to public network addresses on boundary devices such as routes or firewalls to access the Internet, so that there is no need to configure public network IP addresses for every terminal device in the local area network, thus solving the problem of exhaustion of public network IPV4 addresses.

Although NAT solves the problem of IPV4 address exhaustion, ANT technology has its own characteristics. NAT technology can share public IP addresses and be transparent to end users, making the terminal network more secure, but it will also increase the processing capacity of devices such as border routers, resulting in performance degradation, and even hinder the remote access of legitimate programs. From an application point of view, the application scenarios of NAT mainly include the following three aspects:

Many-to-1 conversion: this is also the most common configuration, there are many private IP addresses, only one public network IP address, and then through the normal configuration of NAT to enable a community or a family or a company to access the Internet.

Many-to-one conversion

Many-to-many translation: there are many private IP addresses, corresponding to a lot of public network IP addresses, who uses it first, converts it first, and runs out of it.

1-to-1 translation: that is, a 1-to-1 relationship, with one public address corresponding to one private address, which is mainly used for static mapping of ports.

Finally, to make a summary, what we usually call the intranet is the local area network under a specific environment, such as the local area network connected by several computer devices in the home, and the external network is also known as the Internet, connecting the internetworks of regions, cities and countries. The emergence of NAT technology has solved the problem of exhaustion of IP addresses in the public network, so that computers and other terminal devices can connect to the Internet normally through the configuration of private IP.

This article mainly analyzes how to analyze the relevant knowledge points of intranet, public network and NAT, the content is detailed and easy to understand, the operation details are reasonable, and has a certain reference value. If you are interested, you might as well follow the editor to have a look, and follow the editor to learn more about "how to analyze intranet, public network and NAT".

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