Here’s a look at the widely used version of IPv4.

IP addresses use a uniform format that assigns a logical address to every network and device on the Internet. An IP address is a 32-bit binary number. For the convenience of viewing, it is usually divided into four groups. Each group of eight bits is expressed in a decimal number, forming an address of the shape of 192.168.0.10.

The IP address consists of two parts, a network ID and a host ID, and the two parts are distinguished using a subnet mask. Therefore, a complete IP address must include the host address and the subnet mask two parts to be meaningful, it can be expressed in the following two forms:

  1. 192.168.0.10 Host Address and 255.255.255.0 Subnet Mask: When configuring a network address in Windows, you are asked to enter both values;
  2. 192.168.0.10/24:24 represents the binary bits of the subnet mask. The corresponding decimal grouping is represented as 255.255.255.0. The 255 of three decimal digits is shown here. The simple conversion is 24 (binary bits) / 8 (8 bits in each group) = 3 (group number).

Network ID can be obtained by binary and operation of host address and subnet mask. If you are not familiar with binary arithmetic, you can simply mask the IP address with the corresponding mask portion of 0. For example, if the IP address of class C is 192.168.1.10, the subnet mask 255.255.255.0 is used to mask the fourth group, and the network ID of the host is 192.168.1.0. It is important to note here that the subnet mask does not have to be exactly 255 or 0, 255.255.12.0 for each group. This is also a valid subnet mask.

The addresses for A, B, and C are defined with the following subnet masks.

  • Class A: 255.0.0.0
  • Class B: 255.255.0.0
  • Class C: 255.255.255.0

Private IP address ranges are also defined for internal use within the organization.

  • Class A: 10.0.0.0~10.255.255.255, namely 10.0.0.0/8
  • Class B: 172.16.0.0~172.31.255.255, namely 172.16.0.0/12
  • Class C: 192.168.0.0~192.168.255.255, namely 192.168.0.0/16

These are also the addresses you see the most in your company. The same private address can be used within different organizations because the internal enterprise network is isolated from the Internet and forwarded through routers, and the private address is not directly exposed to the public network.

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