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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.
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.
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]
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:
A /28 route, with a subnet mask of 255.255.255.240, is more specific than a /24 route, with a subnet mask of 255.255.255.0. If the route is of equal specificity to a route already in the routing table, but comes from a more preferred source of routing information, replace the route in the table.
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.
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 .