IPv4 and IPv6 addressing – part 4
30 Jun 2010
Today, the standard methods for moving the network/host address boundary are variable-length subnet masking (VLSM) for host addressing and routing inside a routing domain, and classless interdomain routing (CIDR) for routing between routing domains. (We’ll talk more about routing domains later in this book. For now, think of a routing domain as an ISP’s collection of routers.) And although treated separately here for introductory reasons, it is important to realize that VLSM is the fundamental mechanism of CIDR.
CIDR (defined in RFC 1519) and VLSM (defined in RFC 1860) address more general issues than simple subnetting. We’ve been looking at addresses from the host perspective in this chapter so far. Let’s discuss CIDR from the router perspective.
