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I. brief introduction

In our daily life, we use electronic devices that have the ability to surf the Internet. We all have IP addresses, just like everyone has their own name. The IP address is divided into IPV4 IPV6, and the IP address we are talking about refers to the address of IPV4.

As long as I remember your name, no matter where you are in the world, I will see you.

"your name" by Xin Haicheng

IPV4 (Internet Protocol Version 4)

Interconnection protocol version 4, there is IPV1 IPV2 IPV3 before version V4, there is also IPV5 IPV6,IPV5 has been aborted in the experiment, the replacement of IPV4 will be IPV6. (IPV4 address for example: 192.168.1.1, 114.114.114.114)

Note: the IP we are talking about next refers to the IPV4 address.

1.IP is the name of the electronic equipment room.

To take a simple example, the three giants of the Internet today connect devices to devices and people to people through IP.

What is the IP address?

What we often see is that IP addresses are decimal. What we learned in primary school is decimal.

But the real IP address is actually made up of machine-recognized binary, but in order to facilitate the conversion of human memory to decimal.

Digression: why do people use decimal and machines use binary? In ancient times, primitive people could only count at most two hands (excluding octahedral arhats, three heads and six arms, etc.) after hunting. When the fingers were not enough, they marked them with stones, which created the decimal system. The machine uses the "on" and "off" circuit, which happens to represent 0 or 1, thus forming a binary system.

1. Decimal method of calculation

two。 Binary calculation method

3. Binary conversion decimal

IP addresses are made up of 32-bit binaries, and the conversion to decimal makes it easier to remember.

Composition of 4.IP addresses

The IP address consists of two parts, the network part and the host part, such as:

If the network part is the same, it represents the same network segment (the host part can be different). What is the same network segment (the same broadcast domain)? Just like people in the same room, they can communicate with each other basically by shouting, which is what we call broadcasting. Different network segments are like they can't communicate with each other in different rooms under normal circumstances.

IP addresses are divided into four groups, 8bit (8 binaries), and four groups make up 32 binaries.

Convert binary 1111 to decimal 1111

Binary to decimal

Binary system

1111 1111

Decimal system

two hundred and fifty five

Convert binary 1110 to decimal to 233,

Binary system

1110 1001

Decimal system

two hundred and thirty three

Decimal to binary

Divide 128 by 2 to get the remainder, then divide it down one by one, and then arrange the remainder backwards.

Binary conversion calculator mode

Open the calculator (enter calc in search)

Calculator → View → Scientific

Select decimal, enter 255

Click binary, and then convert the decimal to binary. It's the same thing as converting binary to decimal.

5.IP address Typ

IP address types are A, B, C, D, E,

Class A, B, C: IP addresses of the types commonly used in our lives

Class D: multicast addresses will talk about several commonly used routing protocols, and user multicast addresses will be learned in CCIE.

Class E: for Internet experiments and development only

Note: the first two bits of class An are 0, the first two bits of class B are 10 (other bits are arbitrary), the first three bits of class C are 110 (other bits are arbitrary), the first four bits of class D are 1110 (other bits are arbitrary), and the first five bits of class E are 11110 (any other bits). The first five bits starting with 127and 0 are special addresses

The composition of three types of IP addresses A, B and C

Network part (NETWORK)

Mainframe part (HOST)

I

The scope and function of the P address are as follows:

Special address in IP address

Public and private network addresses

For example, 192.168.1.100 Compact 24

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