User manual

Addressing Schemes B-
7
Supernetting, or CIDR (Classless InterDomain Routing) is a
technique that allows each of these larger networks to be
represented by a single routing table entry, as shown in Figure 3
below.
Figure 3. Sample Supernetting - CIDR - Topology
To do this, supernet addressing does something very different
from traditional TCP/IP routing (which allows only one
netmask per network). In supernet routing, each supernet can
be assigned its own netmask.
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.