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Classless Inter-Domain Routing (CIDR / ˈ s aɪ d ər, ˈ s ɪ-/) is a method for allocating IP addresses for IP routing.The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous classful network addressing architecture on the Internet.
A wildcard mask is a mask of bits that indicates which parts of an IP address are available for examination. In the Cisco IOS, [1] they are used in several places, for example:
Special address blocks Address block Address range Number of addresses Scope Description 0.0.0.0/8 0.0.0.0–0.255.255.255 16 777 216: Software Current (local, "this") network [1]
In the address allocation architecture of the Internet using CIDR and in large organizations, it is necessary to allocate address space efficiently. Subnetting may also enhance routing efficiency or have advantages in network management when subnetworks are administratively controlled by different entities in a larger organization.
The CIDR notation for this group is 224.0.0.0 / 4. [1] The group includes the addresses from 224.0.0.0 to 239.255.255.255 . The address range is divided into blocks each assigned a specific purpose or behavior.
Since the introduction of CIDR, however, the assignment of an IP address to a network interface requires two parameters, the address and a subnet mask. Given an IPv4 source address, its associated subnet mask, and the destination address, a router can determine whether the destination is on a locally connected network or a remote network.
CIDR was designed to permit repartitioning of any address space so that smaller or larger blocks of addresses could be allocated to users. The hierarchical structure created by CIDR is managed by the Internet Assigned Numbers Authority (IANA) and the regional Internet registries (RIRs).
IP addresses in dot-decimal notation are also presented in CIDR notation, in which the IP address is suffixed with a slash and a number, used to specify the length of the associated routing prefix. For example, 127.0.0.1/8 specifies that the IP address has an eight-bit routing prefix, and therefore the subnet mask 255.0.0.0 .