IP address classification dry goods: 5 types of differences, 1 minute to figure out

Hey! Brothers!

As long as your device is connected to the Internet, whether it is a phone, computer or smart watch, it will be assigned a unique identifier - the IP address.

It is the logical location identifier of a device in the network world, allowing data packets to accurately find their destination.

In order to allow the orderly access of massive equipment, IP addresses are scientifically divided into five categories: A, B, C, D, and E. What is the core basis of the classification? What are their characteristics? Don't worry, this article takes you through it quickly!

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01

Disassembling ip addresses: the composition of door plates

An IP address （ such as 192.168.54.4 ） is actually made up of two parts :

· Network ID （ Network ID ） :
The name of the neighborhood you live in （e.g. "Sunshine Gardens"） .All the households in the same neighborhood （devices） share the same network number.

· Host Number (Host ID):

The specific door number of your home （e.g. "404, Building 3"） .It identifies the specific household in the neighborhood （the device） .

Simple formula: IP address = network number + host number

If the area is very large , it is divided into different buildings （ subnets ） , then the formula becomes :

IP address = network number + subnet number + host number

The key dividing criteria: These five categories of ABCDE are mainly based on how many digits of the network number account for the entire address number （or the range of values of the first digit segment） .The more network numbers are occupied, the fewer communities （networks） there are, but the number of households that can live in each community （ host ） it 's a lot .

02

Class A address

The network number is the shortest （ only the first segment ） , the host number is the longest （ the last three segments ） .

Must start with 0 （binary） .Converted to our familiar numbers, that's 1.x.x.x to 126.x.x.x.

Very rare , with only 126 such large communities in the world （ Class A networks ） .

Each A-class community can accommodate about 160 million households （hosts） It's so exaggerated

Usually for real Internet giants like Google, Microsoft, Alibaba, and Tencent.

03

Class B address

Network number medium （ accounting for the first two digit segments ） , host number medium （ accounting for the last two digit segments ） .

Must start with 10 （binary） The number range is 128.0.x.x to 191.255.x.x.

There are more than 16,000 Class B communities.

Each B-class community can accommodate about 65,000 households （ hosts ） .

Generally distributed to networks of not small size such as universities, large enterprises, government agencies and others.

04

Class C address

The network number is the longest （ the first three digits ） , the host number is the shortest （ only the last digit ） .

Must start with 110 （binary） .The numbers range from 192.0.0.x to 223.255.255.x.The most common like 192.168.x.x is a Class C private network address.

Each C-class community can accommodate a minimum of 254 households （host） （why not 256？Explained later）.

Small and medium-sized enterprises, home networks, small networks within schools, etc. are all used, and they are everywhere.

05

Class D address

The beginning is 1110 （binary） .Address range 224.0.0.0 to 239.255.255.255 .

Specifically designed for multicast （Multicast） .Think of it as a neighborhood loudspeaker or a cable TV signal that is broadcast once and a specific group of devices can receive it （e.g., video conferencing, online live streaming） .

It identifies a group of devices that share a protocol, rather than a single host or network.

06

Class E address

The beginning is 1111 （binary） .The address range is 240.0.0.0 to 255.255.255

For the time being, it is mainly reserved for future use or experimentation. Ordinary people and equipment can't use it.

07

Retention Address

· Full zero host number (e.g. 192.168.1.0):  
Refers to the entire network segment itself, like a community name sign.

· Full host number (e.g. 192.168.1.255):
Broadcast address Send a message to this address, the whole neighborhood （network segment） all the residents （devices） can hearBut only in this area, will not run outside.

· 255.255.255.255:  
Ultimate community radio is also valid only in this broadcast domain.

· 127.x.x.x （especially 127.0.0.1） :
This machine loop address 。It is the equipment that sends the message to itself for testing. It is equivalent to talking to myself.

· 0.0.0.0:  
Represents the default route or an unknown address 。You might see it if the computer's IP is in conflict.

· 169.254.x.x:
DHCP gets the failure specific address. When you can't connect to WiFi and don't have a fixed IP, the computer will make up its own address in this range.

08

Public Address vs. Private Address

· Public Internet address:
Only in the world, it is distributed and managed by a dedicated agency, and routers on the internet know it and can find you directly. Limited in quantity and very valuable!

· Private Internet address:
A dedicated door number inside the community! Only valid within your home, company, or campus network. The Internet doesn't recognize them and can't find them. The advantage is that it can be reused and alleviates the shortage of public network addresses. The scope is as follows:

· 10.0.0.0 - 10.255.255.255 （a huge private class A network） 

· 172.16.0.0 - 172.31.255.255 (16Continuous Class B Private Networks） 

· 192.168.0.0 - 192.168.255.255 (256A continuous class C private network, most common!) 

· How do I get online on the private network?
It needs to be done by the router。NAT （Network Address Translation）.Put your internal door number （private network IP） ，Unified conversion to the external address of the public network to send and receive express delivery （data） . 

To summarize the key points:

Determine if same subnet : The two IP addresses and the subnet mask do the "and" operation, and if the result is the same, it is the same block （network segment） neighbors

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