meaning that the mask has that number of 1 bit. This number of 1 bit is called the prefix. In this
case, the mask implied with prefix /27 would be 255.255.255.224.)
customers consuming two whole Class C networks, each consumes a small portion of a single
network. The ISP gets customers to use its IP addresses in a convenient range of values, so
CIDR works well and enables the Internet to grow.
networks called the Internet. So, when designing the IP addressing convention for such a
network, an organization could pick any network number(s) it wanted and use it, and all would
be well. Of course, that's true until the organization decides to connect to the Internet--but that
will be covered later.
a set of IP networks called private Internets, as defined in RFC 1918, "Address Allocation for
Private Internets" (www.ietf.org/rfc/rfc1918.txt). This RFC defines a set of networks that will
never be assigned to any organization as a registered network number. Table 5-25 shows the
private address space defined by RFC 1918.
allowed to advertise these networks as routes into the Internet.
for which there will never be a need for Internet connectivity. So, the dreaded day of exhausting
the registered IP Version 4 network numbers has been delayed again, in part by CIDR and in
part by private addressing.