How to choose a subnet mask

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The network operates more efficiently - less traffic is required, since devices communicate primarily within their own subnet.
How to determine a subnet by IP address
When you send a message, the computer only has the IP address, but it needs to figure out where the network number ends and the device number begins. So it reads the IP and translates it into binary.

IP address: 192.168.1.10

In binary: 11000000.10101000.00000001.00001010

From the first bits of the code, we can draw conclusions about the size of the network:

0 — large network (addresses from 0.0.0.0 to 127.0.0.0);
10 - medium network (address range from 128.0.0.0 to 191.255.0.0);
110 - small network (from 192.0.0.0 to 223.255.255.0).
But it is more convenient and easier to use a subnet mask.

Why do you need a subnet mask?
The subnet mask is similar to the IP - it also includes four parts or 32 bits. With its help you can:

Find network number;
Simplify the process of transferring data between different networks;
Organize the address space correctly.
IP address: 192.168.1.10

Subnet mask: 255.255.255.0

This is what determining a network address by mask and IP looks like :

1) Write the subnet mask 255.255.255.0 in binary form:

11111111.11111111.11111111.00000000

The first 24 bits = 1, meaning they indicate the network number, and the 8 bits at the end are 0, they identify the specific device.

2) Let's write the IP address 192.168.1.10 in binary code:

11000000.10101000.00000001.00001010

Taking into account the subnet mask, we take the first 24 bits (11000000.10101000.00000001), which corresponds to 192.168.1. So this will be our network, and the 10 at the end is the device number.

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A sysadmin is no longer a person who configures computers. Become a strong specialist who supports the company's infrastructure.
The subnet mask shows the number of bits in the network number. For example, 255.0.0.0. is a large network (class A), the number here takes up only 8 bits, and 255.255.255.0 is a small network (class C), the network number is indicated by three numbers at once.

Division of IPv4 addresses into classes
Classification of IPv4 addresses. Source
In class C, the default subnet mask is 255.255.255.0. But it can be configured manually:

1. Determine the size of your network

Calculate how many devices you plan to connect. It is important to take into account all computers, printers, routers, etc.