Lucent Technologies PortMaster - Manual (Page 299)

Networking Concepts A-3
Network Addressing
Class A Addresses
The class A IP address format allocates the highest 8 bits to the network field and sets
the highest-priority bit to 0 (zero). The remaining 24 bits form the host field. Only 126
class A networks can exist (0 is reserved, and 127 is used for loopback networks), but
each class A network can have almost 17 million hosts. No new class A networks can be
assigned at this time.
For example:
Class B Addresses
The class B IP address format allocates the highest 16 bits to the network field and sets
the two highest-order bits to 1 and 0, providing a range from 128 through 191,
inclusive. The remaining 16 bits form the host field. More than 16,000 class B networks
can exist, and each class B network can have up to 65,534 hosts. For example:
10.100.232.1
Network
address
Host address
172.16.232.121
Network
address
Host address