User's Manual

232 Appendix F IP subnetting
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Therefore:
A class C network (8 host bits) can have 2
8
–2 or 254 hosts.
A class B address (16 host bits) can have 2
16
–2 or 65 534 hosts.
A class A address (24 host bits) can have 2
24
–2 hosts (approximately 16 million
hosts).
Since the first octet of a class A IP address must contain a 0, the first octet of a
class A address can have a value of 0 to 127.
Similarly the first octet of a class B must begin with 10, therefore the first octet of
a class B address has a valid range of 128 to 191. The first octet of a class C
address begins with 110, and therefore has a range of 192 to 223.
Table 43 Classes of IP addresses
IP Address: Octet 1 Octet 2 Octet 3 Octet 4
Class A 0 Network number Host ID Host ID Host ID
Class B 10 Network number Network number Host ID Host ID
Class C 110 Network number Network number Network number Host ID
Note: Host IDs of all zeros or all ones are not allowed.
Table 44 Allowed IP address range By class
Class Allowed Range of First Octet (Binary) Allowed Range of First Octet (decimal)
Class A 00000000 to 01111111 0 to 127
Class B 10000000 to 10111111 128 to 191
Class C 11000000 to 11011111 192 to 223
Class D 11100000 to 11101111 224 to 239