234 Appendix F IP subnetting
N0115791
Table 46 shows all possible subnet masks for a class C address using both
notations.
The first mask shown is the class C natural mask. Normally, if no mask is
specified, it is understood that the natural mask is being used.
Example: two subnets
As an example, you have a class C address 192.168.1.0 with subnet mask of
255.255.255.0.
The first three octets of the address make up the network number (class C). You
want to have two separate networks.
Table 46 Alternative Subnet Mask Notation
Subnet mask IP address Subnet mask 1 Bits Last octet bit value
255.255.255.0 /24 0000 0000
255.255.255.128 /25 1000 0000
255.255.255.192 /26 1100 0000
255.255.255.224 /27 1110 0000
255.255.255.240 /28 1111 0000
255.255.255.248 /29 1111 1000
255.255.255.252 /30 1111 1100
Network number Host ID
IP Address 192.168.1. 0
IP Address (Binary) 11000000.10101000.00000001. 00000000
Subnet Mask 255.255.255. 0
Subnet Mask (Binary) 11111111.11111111.11111111. 00000000
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