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:
xxx.xxx.xxx.xxx
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:
Table 9-7
IP address class format
Class
First Address Byte
xxx.
Second Address
Byte xxx.
Third Address Byte
xxx.
Fourth Address Byte
xxx
A
Network.
Host.
Host.
Host.
B
Network.
Network.
Host.
Host.
C
Network.
Network.
Network.
Host.
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.
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Chapter 9 Networking
ENWW
Table 9-8
Network class characteristics
Class
Network Class
Characteristics
Address Range
Maximum Number of
Networks in the Class
Maximum Hosts in
the Network
A
0
0.0.0.0 to
127.255.255.255.
126.
Over 16 Million.
B
10.
128.0.0.0 to
191.255.255.255.
16,382.
65,534.
C
110.
192.0.0.0 to
223.255.255.255.
Over 2 Million.
254.