About IP address

1.IP The address is binary , Only in order to make human beings recognize and read easily, decimal system appears IP Address and domain name ,IP The address is divided into network number and host number , Similar to the regional address and specific house number address in the express address , How to divide the network number and host number? Please Baidu .

2.IP There are five types of addresses ,A/B/C/D/E, D/E Class address is reserved address , Commonly used A/B/C Three types of

3.A Class address range ：1.0.0.0 To 126.255.255.255

​ Reserved address ： 127.0.0.0 To 127.255.255.255

​ B Class address range ：128.0.0.1 To 191.255.255.255

​ C Class address range ：192.0.0.1 To 223.255.255.255

4. Three types of common addresses IP The address has four paragraphs in total 32 It's made up of two digits , Its 32 Bit binary digit conversion point decimal system is common IP Address

​ e.g.：192.168.5.101
1100 0000 1010 1000 0000 0101 0110 0101

5. Calculation method ：

IP Each segment of the address from right to left corresponds to 8 Bit binary number ,

From right to left, each paragraph is from 2 Zero power to 2 Seventh power ,

from IP The address should be converted from left to right 2^7 Start subtracting , Each paragraph is calculated independently ,

Reduce to that one and fill in 1, If the number is less than that, fill in zero ,

Calculated from binary to IP Address, then each bit is 1 Where is the calculation of 2 To the power of ,8 Add bits to get , Be careful 2^0 by 1

            192        168         101         129
 Character occupancy     00000000   00000000    00000000    00000000     This trip is useless, just occupying a place 
 To the power of two     76543210   76543210    76543210    76543210
 Conversion method ： For example, the second paragraph is 168, Then from left to right 2^7 Start subtracting ,168 subtract 2^7 That is to say 128 Can be reduced to , Then the first binary from left to right is 1, more than 40 Then subtract 2^6 That is to say 64 It can't be reduced to , The first binary from left to right is 0, Continue remaining 40 subtract 2^5 That is to say 32, If it can be reduced to, the third binary from left to right is 1, And so on 
 Converted binary   11000000   10101000    01100101    1

6. Of each network segment IP The first place of the address is 192.168.5.0 or 132.154.0.0 Is the network address , The last one is like 192.168.5.255 or 132.154.255.255 For broadcast address , Is an unavailable address , Among them, such as 192.168.5.127 or 132.154.127.127 It is the local loopback website

7. Subnet mask ： Also by 32 Bit binary composition , But and IP The difference in address is that the dotted decimal value of subnet mask can only be 2 To the power of 255/128/64/32/16/8/4/2/.

The first function is to identify the network , It is also divided into network number and host number

The second function is to divide subnets , With C Class address as an example , The subnet mask is 255.255.255.0, Converting to binary is 24 individual 1 and 8 individual 0 That is, common /24 It means that there is no subnet , Each subnet division represents the mask of the subnet. The network number actually borrows a host number , as follows ：

            255        255         255          0
 Character occupancy     00000000   00000000    00000000    00000000     This trip is useless, just occupying a place 
 Power conversion     11111111   11111111    11111111    00000000    /24
 Divide the first subnet , I borrowed one of my network number from my host number , And so on , For each bit borrowed, there are two choices 0 and 1
            255        255         255          128
 Power conversion     11111111   11111111    11111111    10000000    /25