Classless Inter-Domain Routing: Difference between revisions

Revision as of 00:56, 9 November 2005

Revision as of 01:01, 9 November 2005

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Historically, the IP address space was divided into three main '[[classful network|classes of network]]', where each class had a fixed size network address. The class, and hence the length of the network address and the number of hosts on the network, could always be determined from the most significant bits of the IP address. Without any way of specifying a prefix length or a subnet mask, [[routing|routing protocols]] necessarily used the class of the IP address specified in route advertisements to determine the size of the routing prefixes to be set up in the [[routing table]]s.

As the experimental TCP/IP network expanded into the Internet during the 1980s, the need for more flexible addressing schemes became increasingly apparent. This led to the successive development of [[SubnetSubnetwork|subnetting]], Variable-Length Subnetting, and then CIDR. Because the old class distinctions are now ignored, the new system was called '''classless routing'''. This led to the original system being called, by [[back-formation]], '''classful routing'''.

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