© 2006 Cisco Systems, Inc. All rights reserved.
ITE 1 Chapter 6
The Anatomy of an IPv4 Address
For each IPv4 address, some portion of the high-order bits
represents the network address.
•At Layer 3, we define a network as a group of hosts that have
identical bit patterns in the network address portion of their
The number of bits used in this host portion determines
the number of hosts that we can have within the network.
•For example, if we need to have at least 200 hosts in a
particular network, we would need to use enough bits in the
host portion to be able to represent at least 200 different bit
•To assign a unique address to 200 hosts, we would use the
entire last octet. With 8 bits, a total of 256 different bit patterns
can be achieved. This would mean that the bits for the upper
three octets would represent the network portion.