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C5-4 893-741-B
Network Protocols
Network Classes
The Internet protocol divides the address into a network section and a local or host section. The
address has five classes, of which three can be used for hosts such as the Model 5390 server. The
class for the address is determined by the number of bits assigned for the network section of the
address.
• The first address type is Class A and has a 7-bit network number and a 24-bit host address.
This allows 128 Class A networks.
• The second address type is a Class B and has a 14-bit network number and 16-bit host
address. This allows 16,384 Class B networks.
• The third address type is a Class C and has a 21-bit network address and a 8-bit local address.
This allows 2,097,152 Class C networks.
• The fourth and fifth address types are Class D and Class E. These cannot be used for normal
host applications.
Table C5-1 lists the three network classes, the decimal number that appears in the first octet, and
what sections of the Internet address are assigned to the network and to the host. The nnn represents
all or part of the network number and the hhh represents all or part of the host address.
For example, the Internet address 63.000.000.035 is a Class A address; 63 is the network address
and 35 is the host address. With a Class A network, the Internet address can be specified as 63.0.0.35
or 63.35.
Table C5-1. Network Classes
Class First Octet Internet Address
A 1-126 nnn.hhh.hhh.hhh
B 128-191 nnn.nnn.hhh.hhh
C 192-223 nnn.nnn.nnn.hhh
NOTE:
The Class A network 127 is reserved for software loopback; do
not use it as an Internet address.