Classless Inter-Domain Routing

(redirected from IP prefix)

Classless Inter-Domain Routing

(networking)
(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.
Mentioned in ?
References in periodicals archive ?
Since in BGP, the routing messages are generated regarding to every IP prefix.
Moreover, since AS2-AS3 is no longer reachable, AS2 will receive the route withdraws of every IP prefix in AS3; similarly, AS3 will receive the route withdraws of every IP prefix in AS2.
When the user-agent information was combined with just the IP prefix the accuracy was still 79.
For example, replacing an IP address with its IP prefix still yields enough information that when combined with other commonly logged factors can be revealing.
Examples of specific topics address include real-time identification of IP prefix hijacking, cryptanalysis of a cognitive authentication scheme, network flow watermarking attacks on low-latency anonymous communication systems, usable mandatory integrity protection for operating systems, using rescue points to navigate software recovery, optimal communication complexity of multiphase protocols for perfect communication, and multi-dimensional range query over encrypted data.
When making routing changes, a route-optimization solution has the option of rerouting traffic at both the AS level and at the IP prefix level.
Thus if we could restrict IP prefix lengths we could get faster search.
Thus, the challenge becomes how to move from a model that maps a single IP address to a subscriber, to one that maps an IP prefix to a subscriber.
Prefix Length Cutting: after prefix index cutting, we partition rules with the same IP prefix length.
First we choose several specific bits of IP prefix and then group the rules with the same bits.
Besides, it is common that the bits in the IP prefix are definite, i.
In Layer-2, we put the rules with the different IP prefix length in different groups.