Information Technology Reference
In-Depth Information
CIDR
CIDR (classless interdomain routing) is a prefix-based standard for the interpretation of IP addresses.
CIDR allows routing protocols to summarize multiple networks, a block of addresses, as a single
route. With CIDR, IP addresses and their subnet masks are written as four octets, separated by peri-
ods, followed by a forward slash and a number that represents the subnet mask (slash notation). For
example, 172.16.1.0/24.
As you previously learned, route summarization, also known as route aggregation, is the process of
advertising a contiguous set of addresses as a single address with a less-specific, shorter subnet mask.
Remember that CIDR is a form of route summarization and is synonymous with the term
supernetting
.
Calculating a Summary Route Exercises
To review your route summarization skills, complete the following activities. These are simply modifi-
cations of the same exercises from Chapter 2. You can also repeat those exercises for extra practice.
Exercise 1
Referring to Figure 6-13, what summary route would R1 send to BBR for the four networks? Write
your answer in the space provided.
Figure 6-13
Summary Route Exercise 1 (Answer)
192.168.64.0/22
192.168.68.0/22
R1
BBR
192.168.72.0/22
Summary Route
192.168.64.0/20
192.168.76.0/22
