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 region.
- Zeros indicate that part of the address region 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 Neither subnet 0 nor the subnet consisting only of ones may be used. Neither host number 0 nor the host number consisting only of ones may be used! If the IP address is set using the KS2000 configuration software, it is necessary for the subnet mask also to be changed with the KS2000 configuration software. If ARP addressing is used, the associated standard subnet mask, based on the IP address, is entered. Under BootP or DHCP the subnet mask is entered by the server. |