Parameterizing and commissioning
CX8093
29
Version: 1.6
• DNS name: CX-010203
6.2.3
Subnet mask
The subnet mask is subject to the control of the network administrator, and specifies the structure of the
subnet.
Small networks without a router do not require a subnet mask. The same is true if you do not use registered
IP numbers. A subnet mask can be used to subdivide the network with the aid of the mask instead of using a
large number of network numbers.
The subnet mask is a 32-bit number:
• Ones in the mask indicate the subnet part of an address space.
• Zeros indicate that part of the address space which is available for the host IDs.
Description
Binary representation
Decimal representation
IP address
10101100.00010000.00010001.11001000
172.16.17.200
Subnet mask
11111111.11111111.00010100.00000000
255.255.20.0
Network ID
10101100.00010000.00010000.00000000
172.16.16.0
Host ID
00000000.00000000.00000001.11001000
0.0.1.200
Standard subnet mask
Address class
Standard subnet mask (decimal) Standard subnet mask (hex)
A
255.0.0.0
FF.00.00.00
B
255.255.0.0
FF.FF.00.00
C
255.255.255.0
FF.FF.FF.00
Note
Assignment of subnets, host numbers and IP addresses
Neither subnet 0 nor the subnet consisting only of ones may be used. Host number 0, and
the host number consisting only of ones, must not be used. Under BootP or DHCP the sub-
net mask is transmitted also by the server.
