Subnet Prefix

sometimes a lot of confusion at the sight of this ip 192.168.0.0/22, 22 was what? or sometimes when subscribing to an ISP and have allocation of ip address (eg 192.168.0.0/28), how to set?

/ 22 or / 28 is called a prefix, as we know, ipv4 consisted of 4 octed or 32 bits, if we have 192.168.0.0/28 network, meaningful in a 28-bit binary networks (translated by 1) and rest (4 bits) is the host.

to find what ip that can be used 2n-2 ^ 2 = 4 x 2 = 14 hosts, if the 192.168.0.0/28 ip means that it can be in use is 192.168.0.1 to 192.168.0.14, because the 192.168.0.0 in use as network and 192.168.0.15 used as the broadcast.

well, to find the subnet mask from prefix / 28 was, because there are 28 bits network and host the 4-bit binary in writing as follows:

11111111.11111111.11111111.1111 0000

if translated into a decimal, becomes: 255.255.255.240