classless inter-domain routing
(foldoc) | Classless Inter-Domain Routing
CIDR
(CIDR) /sid*r/ A technique that summarises a
block of Internet addresses in a routing table as an
address in dotted decimal notation followed by a {forward
slash} and a two-digit decimal number giving the number of
leading one bits in the subnet mask. For example,
123.123.123.0/24 specifies a subnet mask of
11111111.11111111.11111111.00000000 (binary), implying the
block of addresses 123.123.123.0 through 123.123.123.255.
CIDR is "classless" because it is not limited to the subnet
masks specified by Internet address classes A, B and C.
According to RFC 1519, CIDR was implemented to distribute
Internet address space more efficiently and to provide a
mechanism for IP route aggregation. This in turn reduces
the number of entries in IP routing tables, enabling faster,
more efficient routing, e.g. using routing protocols such
as OSPF. CIDR is supported by BGP4.
See also RFC 1467, RFC 1518, RFC 1520.
(2006-01-26)
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