What is the IP address

In use TCP/IP When communication , use IP Address identification hosts and routers . In order to ensure normal communication , It's necessary to configure each device with the right IP Address , Otherwise, normal communication cannot be realized at all

IPv4

IPv4 Address by 32 Bit composition , common 4 Bytes , People are more used to decimal system , So we convert every byte to decimal , The middle is separated by dots , such as 192.168.1.1

IPv4 How many addresses can be assigned ？2^32 = 4 294 967 296, almost 43 One hundred million , That is to say, at most 43 Hundreds of millions of devices are connected to the network at the same time , And in the 2019 year IPv4 The address is officially exhausted

IP The address is not configured according to the host , In other words, a host can not only have one IP Address , But according to the network card settings IP Address , however , The network card can also set multiple IP, You can also not configure IP Address . It's like a router , There are usually two network cards

Then your computer's IP How is the address assigned ？ Is it distributed at will ？ There are so many devices in the global network ,IP The address is the unique identification of the device , It's impossible to configure it at will , What should I do if I repeat

IP The address is identified by the network （ network address ） And host identification （ The host address ） form

The network identifier is the unique identifier for each segment of the data link , let me put it another way , The network ID is the only network address of a LAN , Every LAN has its own network segment

The host ID is the unique ID of the host in the same LAN , A host in the same LAN cannot have the same host address

thus ：

A mainframe's IP The address is made up of a unique network address + A unique host address makes up a unique IP Address , To ensure the IP The uniqueness of address in global network

How to divide network address and host address ？ There are two ways

• 192.168.1.1/24, The network address has 24 A bit

192.168.1 It's the Internet address ,1 It's the host address

• 192.168.1.1,Netmask 255.255.255.0, Use subnet mask netmask Express

The subnet mask is IP All the network address bits of the address are set to 1, The host address bits are all set to 0, Then each 8 A group of bits , In decimal

IPv4 There are four types of addresses ：

• A Class address

The first is 0, front 8 Bit is the network address , The network address range is 0000 0000 - 0111 1111, Distributable A Class segment is 0.0.0.0 - 127.0.0.0

• B Class address

The first two are 0, front 16 Bit is the network address , Distributable B Class segment is 128.0.0.1 - 191.255.0.0

• C Class address

The first three are 110, front 24 Bit is the network address , Distributable C Class segment is 192.168.0.0 - 239.255.255.0

• D Class address

The top four are 1110, All 32 Bits are all network addresses , Distributable D Class segment is 224.0.0.0 - 239.255.255.255,D Class address has no host address , Suitable for multicast address （ Why? ？）

If you want to configure your host network card IPv4 Address , The host address can't be repeated , It can't be all 0 Or all of them 1, Because it's all 0 Only in IP Use when the address is unknown , And the whole 1 Indicates the broadcast address

although IPv4 The addresses are classified , But it can't be so rigid in practice , It needs to be set flexibly according to the number of hosts in the LAN

such as C The number of hosts with class addresses is 255, And I want to build a LAN within the host only 50 individual , Then I use C Class addresses waste resources , What shall I do? ？ Network address and host address can be flexibly divided , To meet the actual use . By what ？ Subnet mask

For example, there are at most 50 Console host , use C Class address waste , The host address bit can be shortened appropriately , from C Class 8 individual bit Shorten to 6 individual ,2^6 = 63, At most configurable 63 Host computer , The corresponding network address bit is 26 position

The subnet mask is 255.255.255.192

IPv6

In order to solve IPv4 The problem of address exhaustion ,IPv6 emerge as the times require

IPv6 yes IPv4 Of 4 times , from 128 It's made up of two bits , common 16 Bytes , and IPv4 use 10 Hexadecimal means different ,IPv6 per 16 Bit is a group. , use 16 Hexadecimal said , The middle is separated by a colon , such as ：DEAF:2780:3A4E:0189:C3D5:F728:6B23:1011

that IPv6 How many addresses can be assigned ？2^128, It's said that one can be assigned to every grain of sand on the earth IPv6 The address of

IPv6 No, ABCD Class address , There is no subnet mask , Its addressing method is not ARP Addressing , Those who are interested can understand by themselves , I don't know much

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