About 192.168.0.0/24 and CIDR

About 192.168.0.0/24 and CIDR, this is actually a CIDR block, or a Subnet, in the form of Classless and Subnet Address Extensions and Supernetting. We know that to determine a subnet, we need to know the host address and subnet mask, but in the form of CIDR, we can simply get two values. For example, "192.168.0.0/24" indicates that the IP address of this network segment starts from 192.168.0.1 and ends at 192.168.0.254 (192.168.0.0 and 192.168.0.255 have special meanings and cannot be used as IP addresses). The subnet mask is 255.255.255.0. How does the above subnet mask come from? In fact, the key lies in "24. We know that the IP address is composed of four decimal numbers, which is equivalent to 32-bit binary. In CIDR format, the last digit separates the 32 bits (taking 24 as an example): the first 24 bits are represented by "1", and the last 8 bits are represented by 0, we can get a binary number: 11111111 11111111 11111111 00000000. Convert it to decimal, that is, 255.255.255.0.