What is an IP address?

IP is the abbreviation of Internet Protocol, namely network Interconnection protocol. The IP address is represented by the binary, each IP address length 32bit, the bit translates into Byte, is 4 byte, but the binary system is the computer data processing pattern, does not conform to people's daily use habit, therefore the IP address often is written in the decimal form, the middle uses the symbol "." Separates different bytes.

IP address has IPv4 and IPv6 two kinds, but the current widely used or IPV4 address, so this article will focus on IPV4 address, IPV6 address is to address the exhaustion of IPV4 addresses a solution, in the domestic use of less, here do not introduce more.

IPV4 address addresses can be divided into two categories depending on purpose and security:

1, public (network) Address: Public IP address can be used in public network (extranet), the use of public address computers can access each other through the Internet.

2, private address: Private address can only be sufficient in the local area network (intranet), the use of private address of the computer can not access through the intern.

We can liken a common IP address to a normal mobile phone number, while a private IP address can be likened to a V-net or a home network-assigned cornet, such as 520, 521, and so on. Ordinary mobile phone numbers can be talked to each other, but the home network No. 520 code can not and home network number of calls, only to call the home network of 521 cornet, to communicate with other numbers can only use 520 of the corresponding mobile phone number.

Public network IP address and the use of private IP address is the same, the use of public address computers can communicate with each other; computers in the same local area network can communicate by using private addresses, but access to resources on the Internet requires the use of a public network IP address.

Depending on the number of host digits in the identified network, these 5 categories are classified as a, B, C, D, and E:

Interim Class A addresses are allocated to government agencies for use; B-Class address assigned to large and medium-sized companies to use (Microsoft, Google, IBM and other types of enterprises); Class C addresses are assigned to any person in need; Class D addresses are multicast; Class E addresses reserved for use in scientific research and teaching. Usually we get through ADSL Internet account IP address is the C class address.

Range of Address of Class A: 1.0.0.1---126.255.255.254, interim 10.0.0.1---10.255.255.254 the address of the scope class as a private address; 127.x.x.x is used as a looping test (often used for network scheduling).

Class B address range: 128.0.0.1---191.255.255.254, interim 172.16.0.0---172.31.255.254 as a private address, 169.254.x.x as a reserved address, The computer automatically obtains the address of the network segment for the configuration of any IP address.

Class C address range: 192.0.0.1---223.255.255.254, interim 192.168.0.1---192.168.255.255 is a private address.

Scope of Class D addresses: 224.0.0.1---239.255.255.254

Range of Class E addresses: 240.0.0.1---255.255.255.254

If you are using a router to dial Internet via ADSL, the IP address obtained by the routed Wan is a C-class public address, and the IP address assigned to the computer by default belongs to the C class private address, but the user can modify it in the management page of the router, which can be modified to the private address of A and B.

Computers must obtain an IP address before they can access resources on the Internet, IP addresses are generally provided by ISP operators, that is, mobile, unicom, telecommunications broadband providers.