CIDR (Classless Inter-Domain Routing)

CIDR (Classless Inter-Domain Routing) on ​​the Internet is a way to create additional address, these addresses are provided to the service provider (ISP), and then assigned by the ISP to the customer. CIDR routing together, so that the backbone of an IP address on behalf of thousands of service providers, IP address, thereby reducing the burden on Internet routers.Basic InformationAbbreviation: CIDR (Classless InterDomain Routing)Category: Network and exchangeExplanation: The current IPv4 (Internet Protocol version 4) address has been exhausted, this is a made to solve the address exhaustion as a measure. It is the combination of several IP networks, use of a classless inter-domain routing algorithm can reduce the core router from the routing information carried in the number.All information sent to these addresses as packets are sent to MCI or Sprint and other ISP. In 1990, Internet routing on about 2000. After five years, Internet has more than 30,000 routes. If no CIDR, routers can not support the increase in Internet sites. CIDR uses variable 13 to 27 network ID, network ID instead of class ABC used a fixed 8, 16 and 24.How it worksCIDR worksCIDR is used on the original distribution of Class A, B and C categories routing address has been re-building process. CIDR prefix length with 13-27 bit address instead of the original structure of some of the restrictions on the network address (the address of the network portion of the three categories were limited to 8-bit, 16-bit and 24-bit). The administrator can assign the address block, the number of the host range of 32-500,000, so that it can better meet the special needs of institutions to address.
 CIDR address includes the standard 32-bit IP address and the network prefix bits of information. A CIDR address 222.80.18.18/25, for example, where "/ 25" that its previous address in the top 25 on behalf of the network part, the remaining representatives from the host portion.CIDR was established in the "super network" based on "super network" is "subnetting" of the derivative, can be seen as the reverse process of subnetting. When subnetting, some borrow from the host address, part of its merger into the network; in super-network, the network part of some bit sucked into the host part of the merger. This is no super-class networking technology by a group of small non-network aggregation to a larger category of a single routing table entry, reducing the domain of Internet routing number routing table entries.InstanceFor example, an ISP is assigned a number of Class C network, the ISP is prepared to the class C network assigned to each user group, has been assigned three Class C network segment to the user, if not the implementation of CIDR technology. ISP's router's routing table there will be three entries under the networking section of the route, and will inform it to the router on the Internet through the implementation of CIDR technology, we can put in the ISP's router three segments 198.168.1.0,198.168.2.0,198.168 .3.0 converging route 198.168.0.0/16. so the ISP router to the Internet only this one notice 198.168.0.0/16 route, greatly reducing the number of routing table thus saving a router for the network storage space. It is noteworthy that the use of technology convergence CIDR network address bits must be consistent, in the example above, if the ISP connection on the example of a 172.178.1.0 network segment, the network route will not be together, not implement CIDR technology.