After you have received your network number, you can then plan how to assign the host parts of the IPv4 address.
The following table shows the division of the IPv4 address space into network and host address spaces. For each class, "range" specifies the range of decimal values for the first byte of the network number. "Network address" indicates the number of bytes of the IPv4 address that are dedicated to the network part of the address, with each byte represented by xxx. "Host address" indicates the number of bytes dedicated to the host part of the address. For example, in a class A network address, the first byte is dedicated to the network, and the last three are dedicated to the host. The opposite is true for a class C network.
Table 5-1 Division of IPv4 Address Space
Class |
Range |
Network Address |
Host Address |
---|---|---|---|
0-127 |
xxx |
xxx.xxx.xxx |
|
128-191 |
xxx.xxx |
xxx.xxx |
|
192-223 |
xxx.xxx.xxx |
xxx |
The numbers in the first byte of the IPv4 address define whether the network is class A, B, or C and are always assigned by the InterNIC. The remaining three bytes have a range from 0-255. The numbers 0 and 255 are reserved; you can assign the numbers 1-254 to each byte depending on the network number assigned to you.
The following table shows which bytes of the IPv4 address are assigned to you and the range of numbers within each byte that are available for you to assign to your hosts.
Table 5-2 Range of Available Numbers
Network Class |
Byte 1 Range |
Byte 2 Range |
Byte 3 Range |
Byte 4 Range |
---|---|---|---|---|
0-127 |
1-254 |
1-254 |
1-254 |
|
128-191 |
Preassigned by Internet |
1-254 |
1-254 |
|
192-223 |
Preassigned by Internet |
Preassigned by Internet |
1-254 |