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   IP addresses are unique identifiers assigned to hosts in computer networks. An IPv4 addresses is a 32-bit number. This bit sequence is divided into two groups. The most significant bits are the network prefix, which defines the subnet address. The group of less significant bits defines the host address on that subnet. Such an address is the basis for routing the transfer of data packets between networks.
CIDR (Classless Inter-Domain Routing) is a classless IP addressing system that replaced the former system based on classes A, B, and C. CIDR uses so-called masks, which determine how many of the most significant bits of the IP address are part of the subnet address. The remaining bits are used to indicate the host address in a given subnet. A CIDR IP address looks like a normal IP address, except it ends with a slash followed by a number.