IP is the Internet Protocol abbreviation, namely Internet Protocol.IP address in binary representation, each IP address is 32bit long, is converted into bit bytes, 4 bytes, but is binary computer data processing mode, does not meet the people’s daily habits, so the IP address is often written in decimal form, intermediate symbol “.” a separate byte.

This article will make ordinary users understand what IP address is through simple and easy to understand narration. Users will be very easy to set up routers when they understand the knowledge.

There are two kinds of IP addresses, IPv4 and IPv6, but IPv4 addresses are widely used. So this article will focus on IPv4 address. IPv6 address is a solution to deal with the exhaustion of IPv4 address.

IPv4 address addresses can be divided into two categories according to their use and security:
1, public (net) address: a public IP address can be used in a public network (an external network), and a computer using a public address can be accessed to each other through the Internet.

2, private address: private addresses can only be used in a LAN (intranet), and a computer using a private address can not be accessed through a intern.

We can take the public IP address compared to ordinary mobile phone number; and private IP address can be likened to the V distribution network or home network cornet, such as 520, 521 etc.. Between the ordinary mobile phone number can call each other, but the number 520 outside the home network and home network can not only be able to call the phone number, home network of 521 mobile phone number to the cornet, and other communication number can only use 520 correspondence.

The use of public network IP address and private IP address is also the same. The computers that use the public address can communicate with each other. The computer in the same LAN can use the private address to realize communication, but if we want to access the resources on the Internet, we must use the public network IP address.

According to the number of host digits in the identification network, 5 types of A, B, C, D and E can be divided.

The middle class a addresses are allocated to the government offices; the B class addresses are allocated to large and medium-sized companies, such as Microsoft, Google, IBM and other types of enterprises, C class addresses are allocated to anyone in need, D class addresses are multicast and E class addresses are reserved for scientific research teaching. The IP address we get through the ADSL internet account is the C address.

A range of addresses: 1.0.0.1—126.255.255.254, as a private address 10.0.0.1—10.255.255.254 address range in 127.X.X.X as the test cycle; (often used when debugging network).

The range of B class address is 128.0.0.1—191.255.255.254, 172.16.0.0—172.31.255.254 in phase 172.16.0.0—172.31.255.254 is private address, 169.254.X.X is reserved address, and the computer automatically gets the address of the segment when any IP address is configured.

The scope of the C class address: 192.0.0.1—223.255.255.254, in the midterm 192.168.0.1—192.168.255.255 is a private address.

The scope of the D class address: 224.0.0.1—239.255.255.254
The scope of the E class address: 240.0.0.1—255.255.255.254

If you use the Internet router through the ADSL dial, then routing the WAN port access IP address is a class C public address; and the router is assigned to the IP address of the computer by default belongs to the C class private address, but the user can modify the router management page, you can modify the A and B private address.

Computers must acquire an IP address before they can access resources on the Internet. IP addresses are generally provided by ISP operators, namely mobile, Unicom and telecom broadband providers.