Classless Inter-Domain Routing: Difference between revisions

Revision as of 11:55, 26 March 2025

Revision as of 19:51, 26 March 2025

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* {{IPaddr|198.51.100.14|24}} represents the IPv4 address {{IPaddr|198.51.100.14}} and its associated network prefix {{IPaddr|198.51.100.0}}, or equivalently, its subnet mask {{IPaddr||24|netmask=dotted}}, which has 24 leading ''1''-bits.

* the IPv4 block {{IPaddr|198.51.100.0|22}} represents the 1024 IPv4 addresses from {{IPaddr|198.51.100.0}} to {{IPaddr|198.51.103.255}}.

* the IPv6 block {{IPaddr|2001:db8::|48}} represents the block of IPv6 addresses from {{IPaddr|2001:db8:0:0:0:0:0:0}} to {{IPaddr|2001:db8:0:ffff:ffff:ffff:ffff:ffff}}.

* {{IPaddr|::1|128}} represents the IPv6 [[loopback]] address. Its prefix length is 128 which is the number of bits in the address.

In IPv4, CIDR notation came into wide use only after the implementation of the method, which was documented using [[dotted-decimal]] subnet mask specification after the slash, for example, {{IPaddr|192.24.12.0|22|netmask=dotted}}.<ref name="RFC 1519" /> Describing the network prefix width as a single number ({{IPaddr|192.24.12.0|22}}) was easier for network administrators to conceptualize and to calculate. It became gradually incorporated into later standards documents<ref>{{cite ietf |rfc=1878 |title=Variable Length Subnet Table For IPv4 |author1=T. Pummill |author2=B. Manning |date=December 1995}}</ref><ref>{{cite ietf |rfc=2167 |title=Referral Whois (RWhois) Protocol V1.5 |author1=S. Williamson |author2=M. Kosters |author3=D. Blacka |author4=J. Singh |author5=K. Zeilstra |date=June 1997 |quote=IP networks are also lexically hierarchical labels using the Classless Inter-Domain Routing (CIDR) notation, but their hierarchy is not easily determined with simple text manipulation; for example, 198.41.0.0/22 is a part of 198.41.0.0/16, which is a part of 198.40.0.0/15.}}</ref> and into network configuration interfaces.