USRobotics NETServer/8 - Manual (Page 234)

B-6 Addressing Schemes
CIDR - Each Supernet is treated as a single entity
Since supernet addressing is a fairly complex mechanism, the
easiest way to understand it is to walk through the setup
process.
Step 1 - Select a netmask for each supernet
Each supernet must have a netmask assigned to it. The netmask
for an individual supernet can be, but does not have to be, the
same as the netmask for any other supernet.
As in subnetting, a netmask creates a division between the
network portion of an address and the host portion of an
address. However, since the network you are defining is larger
than a Class C network, the division you are creating is not in
the fourth octet of the address. For this example, we’ll be
creating supernets composed of fewer than 254 Class C net-
works. So, their netmasks will actually be splitting up the third
octet in their IP addresses.