It's called CIDR (Classless Inter-Domain Routing) notation. It's also commonly referred to as the prefix length. The number after the slash represents the number of consecutive 1's in the subnet mask. For example, is equal to the network with a subnet mask.

Proper format of IP Address range in Security/Blacklist. Question asked by Christian Hansen - Today at 7:00 AM. Unanswered Hi, What is the proper format of an IP Address range in the Security -> Blacklist section? I have been using this format: XXX.XXX.XXX.XXX - XXX.XXX.XXX.XXX CIDR notation explained: CIDR format,CIDR table and The IP addresses were originally divided into five classes. If a company wanted to be connected to the internet, it had to choose an IP address from the appropriate class. For each class, different numbers of octets (the four numerical blocks of IP addresses) were used to identify the networks. IPv4 - Wikipedia

IP Address Classes and Definition Explained

IP address format: Class A Class B Class C Class D Network ID Host ID Network ID Network ID Host ID Host ID Multicast Address 0 1 11 111 0 0 0 14 724 16 21 8 28 Dotted decimal notation: 10000000 00001011 00000011 00011111 ↔ Symbolic name to IP address …

Gheorgheni IP Address Blocks - XMyIP - IP Addresses by City

An IP address made it possible in the past to determine which class it belonged to. For example, the class C networks were located between the addresses and A subnet mask (e.g. is like a mask on top of the IP address and specifies the hosts. In CIDR format, this information is stored as a suffix in the