Differences and functions between intranet IP and public IP

Hello everyone , I meet you again , I'm your friend, Quan Jun .

Intranet IP And the public network IP The difference and function of

Reference link ：https://baijiahao.baidu.com/s?id=1665320351852255921&wfr=spider&for=pc

explain ： This article is only a vernacular commentary on network knowledge ignorant personnel , It is not a technical discussion or advanced article , The officials will choose by themselves ; This article only uses ipv4 Based on .

People who use the Internet will inevitably come into contact with IP Address ,ip The address is divided into intranet （ private ）ip And the public network ( Extranet )ip Address , So what's the difference between them ？ Why should it be divided into intranet and extranet ip？ When to use which ip Today I will use the form of vernacular , Let me give you an example , I hope I can help you to ip Have a preliminary understanding .

Take a family for example , Generally, your router is within , It's the intranet , And all devices or terminals connected in the router will be assigned an intranet ip; conversely , Routers and beyond are extranets ip, This extranet ip Usually in the router WAN On the mouth . If your router uses transparent mode 、 The bridging mode is not explained in this article .

So no matter the Intranet ip Or the Internet ip Are displayed in dotted decimal form, such as 192.168.1.1, This 192.168.1.1 It's the intranet ip, Let me make a list , Show all the current ipv4 Classification of addresses

【1】A Class address ：1.0.0.0~127.255.255.255

【2】B Class address ：128.0.0.0~191.255.255.255

【3】C Class address ：192.0.0.0~223.255.255.255

【4】D Class address ：224.0.0.0~239.255.255.255

【5】E Class address ：240.0.0.0~255.255.255.255

1、A Class address range ：1.0.0.1—126.155.255.254（127.0.0.1 To keep the address , Generally used for loopback addresses ）

①10.x.x.x It's a private address （ The so-called private address is not available on the Internet , Addresses used in local area networks ）.

②127.x.x.x It's a reserved address , Used for cycle test

2、B Class address range ：128.0.0.1—191.255.255.254

① 172.16.0.0—172.31.255.255 It's a private address

② 169.254.x.x It's a reserved address . If IP The address is automatically obtained IP Address , And there is no available one on the network DHCP The server , You'll get one of them IP.

3、C Class address range ：192.0.0.1—223.255.255.254

① 192.168.0.0–192.168.255.255 It's a private address

4、D Class address range ：224.0.0.1—239.255.255.254

5、E Class address range ：240.0.0.1—255.255.255.254

The key is coming. ： Said along while , Maybe I am a little confused about ignorant personnel , In fact, in the above list, you only need to remember which network segment belongs to the intranet （ private ） Which belong to the public network （ Extranet ） That's enough .

The red circle belongs to the intranet , Outside is the public network

So why should we divide the intranet and the extranet ip Well ？ Simply because ip Address （ipv4） Limited quantity and management needs .

Here are some concrete examples , If we put ip The address is regarded as the address of the receiver filled in our daily express delivery , It may be easier to understand .

For example, we need to send a letter to X province X City X District X Avenue 9 Number X community 1 building 1 unit 101 room , So among them “X province X City X District X Avenue 9 Number ” It can be understood as public network ip,“X community 1 building 1 unit 101 room ” It can be understood as intranet ip.

Just imagine , If we want to send someone a letter , Just write “X community 1 building 1 unit 101 room ”, Then no one can find where this community is , Is it right? ？ In turn, , We just write “X province X City X District X Avenue 9 Number ”, Who should the letter be addressed to ？ Who is in which building, which floor and which number ？ No one knows . In other words, the public network ip You can find it at this address , Intranet ip Who will receive .

Someone asked , There may be 1 building ,2 building , Each building has 1 unit ,2 unit , Each unit has 101, How to distinguish ？ Know the intranet and the public network ip 了 , How do we communicate ？ This involves the gateway 、 Routing and other deeper knowledge , We'll talk later .

Publisher ： Full stack programmer stack length , Reprint please indicate the source ：https://javaforall.cn/133029.html Link to the original text ：https://javaforall.cn