Solaris™ 9 Network Administrator Exam Cram™ 2 (Exam CX-310-044)

Classless InterDomain Routing (CIDR)

Classless InterDomain Routing, or CIDR, is a way of grouping networks together for routing purposes across the Internet between domains. With the IPv4 address space running out, CIDR makes much more effective use of the available addresses. CIDR is also known as supernetting, where a number of network addresses are treated as a single address (as opposed to subnetting, where a single network address is divided into smaller networks).

CIDR works by using classless addresses, unlike IPv4, which uses classful addressing. For routing purposes, a single classless address can represent an aggregation of networks (in the same way that the telephone system uses area codes). A CIDR network address looks like this: ...