IP address structure and class
An IP address is comprised of 32 bits of information and divided into 4 sections containing 1 byte
each section or 4 bytes total:
For efficiency in routing, networks were broken down into three classes, so routing can begin simply
by identifying the leading byte of information in the IP address. The three IP addresses that InterNIC
assigns are class A, B, and C. The network class determines what each of the four IP address
sections identify as shown below:
IP address class format
First Address Byte
Third Address Byte
Fourth Address Byte
As illustrated in
Table 9-8 Network class characteristics
, each network class differs by the leading bit
identifier, the address range, the number of each type available, and the maximum number of hosts
each class allows.
Chapter 9 Networking
Network class characteristics
Maximum Number of
Networks in the Class
Maximum Hosts in
Over 16 Million.
Over 2 Million.