CIDR

Background and History of CIDR CIDR (Classless Inter-Domain Routing) was officially introduced by the IETF in 1993 through RFC 1517, RFC 1518, and RFC 1519 to overcome the serious limitations of the existing class-based IP address allocation method, and later revised as RFC 2050 in 1998 to become the internet routing standard. From the late 1980s, as the internet grew rapidly, the existing classful addressing system faced two serious problems. First, Class C networks (254 hosts) were too small and Class B networks (65,534 hosts) were too large, not matching actual needs and wasting large amounts of IP addresses. Second, internet routing tables exploded, causing overload on router memory and processing performance. CIDR solved these problems by completely removing the class concept and introducing Variable Length Subnet Mask (VLSM) to allow precise adjustment of network sizes as needed, and enabled dramatic reduction in routing table size through route aggregation or supernetting techniques that consolidate multiple small networks into a single routing entry. ...