Classless Inter-Domain Routing (CIDR) notation is a method used to express IP addresses and their associated routing prefix information in a more flexible and efficient manner. In CIDR notation, an IP address is followed by a forward slash ("/") and a numerical prefix, indicating the number of bits used for the network portion of the address. For example, the CIDR notation "192.168.1.0/24" represents the IP address 192.168.1.0 with a subnet mask of 255.255.255.0. The "/24" signifies that the first 24 bits are dedicated to the network, allowing for 256 possible host addresses within that subnet.

 

CIDR notation provides a scalable way to allocate and manage IP addresses by allowing for variable-length subnetting. This flexibility is particularly valuable in the modern internet landscape, where address space conservation is crucial. CIDR notation simplifies the representation of IP address blocks, making it easier for network administrators and routers to handle routing table entries efficiently. The adoption of CIDR has played a significant role in optimizing IP address allocation and routing in the global Internet Protocol (IP) infrastructure.