Detailed explanation of network layer

IP Address classification

A

Maximum network number ：127----01111111

Number of allocable networks ：2^7-2=126

The network number is converted into hexadecimal , Number of networks that can be allocated —— Multiple 2 Multiply

B,C equally

B

specially B The value of the first byte of the class address is in the range of 10000000——10111111（ Binary representation ）, Convert binary to 10 Hexadecimal is 128~191 了 .

The function of subnet mask

In order to allocate the same network number to different subnets , The subnet number is used to distinguish the networks of different subnets .

network address

All host numbers are 0( The subnet number is not included )

The Internet address is IP Of the subnet to which the address belongs IP Address ( network address --> subnet IP)

Broadcast address

All host numbers are 1

private IP Address and public IP Address

In the process of use, it is not a A corresponding , Because there are port numbers

The physical layer ---- Solve the problem of materials between hardware devices , voltage , Frequency and other hardware circuit problems

Data link layer --- Solve the problem of how data packets are transmitted in a network (MAC Address )

The network layer ---- Solve the problem of data transmission between different networks (IP Address , Router )